diff --git a/examples_state_test.go b/examples_state_test.go
index 68699fc..68dfef5 100644
--- a/examples_state_test.go
+++ b/examples_state_test.go
@@ -16,8 +16,11 @@ import (
 type Chunks []string
 
 func (l *Chunks) AddChopped(s string, chunkSize int) *parsekit.Error {
+	c, a := parsekit.C, parsekit.A
+	chunkOfRunes := c.MinMax(1, chunkSize, a.AnyRune)
+
 	parser := parsekit.NewParser(func(p *parsekit.ParseAPI) {
-		for p.On(parsekit.C.MinMax(1, chunkSize, parsekit.A.AnyRune)).Accept() {
+		for p.On(chunkOfRunes).Accept() {
 			*l = append(*l, p.BufLiteral())
 			p.BufClear()
 		}
diff --git a/parsehandler.go b/parsehandler.go
index 001d297..d85709d 100644
--- a/parsehandler.go
+++ b/parsehandler.go
@@ -44,19 +44,18 @@ func (p *ParseAPI) panicWhenStoppedOrInError() {
 	if !p.isStoppedOrInError() {
 		return
 	}
-	// No error handling, because it's private known-to-work use only.
-	pc, _, _, _ := runtime.Caller(1)
-	call := runtime.FuncForPC(pc)
-	pc, _, _, _ = runtime.Caller(2)
-	caller := runtime.FuncForPC(pc)
+
+	called, _ := p.getCaller(1)
+	parts := strings.Split(called, ".")
+	calledShort := parts[len(parts)-1]
+	caller, filepos := p.getCaller(2)
 
 	after := "Error()"
 	if p.stopped {
 		after = "Stop()"
 	}
-	parts := strings.Split(call.Name(), ".")
-	name := parts[len(parts)-1]
-	panic(fmt.Sprintf("Illegal call to ParseAPI.%s() from %s: no calls allowed after ParseAPI.%s", name, caller.Name(), after))
+
+	panic(fmt.Sprintf("Illegal call to ParseAPI.%s() from %s at %s: no calls allowed after ParseAPI.%s", calledShort, caller, filepos, after))
 }
 
 func (p *ParseAPI) isStoppedOrInError() bool {
@@ -64,13 +63,11 @@ func (p *ParseAPI) isStoppedOrInError() bool {
 }
 
 func (p *ParseAPI) checkForLoops() {
-	pc, file, line, _ := runtime.Caller(2)
-	id := fmt.Sprintf("%s:%d", file, line)
-	if _, ok := p.loopCheck[id]; ok {
-		caller := runtime.FuncForPC(pc)
-		panic(fmt.Sprintf("Loop detected in parser in %s at %s", caller.Name(), id))
+	caller, filepos := p.getCaller(2)
+	if _, ok := p.loopCheck[filepos]; ok {
+		panic(fmt.Sprintf("Loop detected in parser in %s at %s", caller, filepos))
 	}
-	p.loopCheck[id] = true
+	p.loopCheck[filepos] = true
 }
 
 // peek returns but does not advance the cursor to the next rune in the input.
@@ -109,3 +106,11 @@ func handleRuneError(r rune, w int) (rune, int, bool) {
 	}
 	return r, w, true
 }
+
+func (p *ParseAPI) getCaller(depth int) (string, string) {
+	// No error handling, because we call this method ourselves with safe depth values.
+	pc, file, line, _ := runtime.Caller(depth + 1)
+	filepos := fmt.Sprintf("%s:%d", file, line)
+	caller := runtime.FuncForPC(pc)
+	return caller.Name(), filepos
+}
diff --git a/parsehandler_on.go b/parsehandler_on.go
index 16e9b1d..2bc22d5 100644
--- a/parsehandler_on.go
+++ b/parsehandler_on.go
@@ -43,7 +43,7 @@ func (p *ParseAPI) On(tokenHandler TokenHandler) *ParseAPIOnAction {
 	// Perform the matching operation.
 	m := &TokenAPI{p: p}
 	if tokenHandler == nil {
-		panic("internal parser error: tokenHandler argument for On() is nil")
+		panic("ParseHandler bug: tokenHandler argument for On() is nil")
 	}
 	ok := tokenHandler(m)
 
diff --git a/parsehandler_routing.go b/parsehandler_routing.go
index d6167df..4c26c21 100644
--- a/parsehandler_routing.go
+++ b/parsehandler_routing.go
@@ -10,10 +10,18 @@ import "fmt"
 // or the parser was stopped (using ParseAPI.Stop()).
 func (p *ParseAPI) Handle(parseHandler ParseHandler) bool {
 	p.panicWhenStoppedOrInError()
+	p.panicWhenParseHandlerNil(parseHandler)
 	parseHandler(p)
 	return !p.isStoppedOrInError()
 }
 
+func (p *ParseAPI) panicWhenParseHandlerNil(parseHandler ParseHandler) {
+	if parseHandler == nil {
+		caller, filepos := p.getCaller(2)
+		panic(fmt.Sprintf("ParseAPI.Handle() called with nil input from %s at %s", caller, filepos))
+	}
+}
+
 // Expects is used to let a ParseHandler function describe what input it is
 // expecting. This expectation is used in error messages to provide some
 // context to them.
@@ -41,7 +49,6 @@ func (p *ParseAPI) Stop() {
 }
 
 // ExpectEndOfFile can be used to check if the input is at end of file.
-// Intended use:
 //
 // When it finds that the end of the file was indeed reached, then the
 // parser will be stopped through ParseAPI.Stop(). Otherwise unexpected
diff --git a/parsehandler_test.go b/parsehandler_test.go
index 487a39e..2f8a1c7 100644
--- a/parsehandler_test.go
+++ b/parsehandler_test.go
@@ -12,7 +12,7 @@ func TestGivenNilTokenHandler_WhenCallingOn_ParsekitPanics(t *testing.T) {
 	})
 	RunPanicTest(t, PanicTest{
 		func() { p.Execute("") },
-		"internal parser error: tokenHandler argument for On() is nil"})
+		`ParseHandler bug: tokenHandler argument for On\(\) is nil`})
 }
 
 func TestGivenStoppedParser_WhenCallingHandle_ParsekitPanics(t *testing.T) {
@@ -25,9 +25,8 @@ func TestGivenStoppedParser_WhenCallingHandle_ParsekitPanics(t *testing.T) {
 	})
 	RunPanicTest(t, PanicTest{
 		func() { p.Execute("") },
-		"Illegal call to ParseAPI.Handle() from git.makaay.nl/mauricem/go-parsekit_test." +
-			"TestGivenStoppedParser_WhenCallingHandle_ParsekitPanics.func2: " +
-			"no calls allowed after ParseAPI.Stop()"})
+		`Illegal call to ParseAPI.Handle\(\) from .*ParsekitPanics.func.* at ` +
+			`.*/parsehandler_test.go:\d+: no calls allowed after ParseAPI.Stop\(\)`})
 }
 
 func TestGivenParserWithError_WhenCallingHandle_ParsekitPanics(t *testing.T) {
@@ -40,9 +39,8 @@ func TestGivenParserWithError_WhenCallingHandle_ParsekitPanics(t *testing.T) {
 	})
 	RunPanicTest(t, PanicTest{
 		func() { p.Execute("") },
-		"Illegal call to ParseAPI.Handle() from git.makaay.nl/mauricem/go-parsekit_test." +
-			"TestGivenParserWithError_WhenCallingHandle_ParsekitPanics.func2: " +
-			"no calls allowed after ParseAPI.Error()"})
+		`Illegal call to ParseAPI\.Handle\(\) from .*ParsekitPanics\.func2 at ` +
+			`.*/parsehandler_test\.go:\d+: no calls allowed after ParseAPI\.Error\(\)`})
 }
 
 func TestGivenFilledStringBuffer_BufInterpreted_ReturnsInterpretedString(t *testing.T) {
@@ -102,9 +100,7 @@ func TestGivenLoopingParserDefinition_ParserPanics(t *testing.T) {
 	parser := parsekit.NewParser(looper.first)
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("Het houdt niet op, niet vanzelf") },
-		"Loop detected in parser in git.makaay.nl/mauricem/go-parsekit_test." +
-			"(*parserWithLoop).second at /home/ubuntu/Projects/Parsekit/go-parsekit" +
-			"/parsehandler_test.go:87"})
+		`Loop detected in parser in .*\(\*parserWithLoop\).second at .*/parsehandler_test\.go:\d+`})
 }
 
 // This test incorporates an actual loop bug that I dropped on myself and
@@ -129,7 +125,12 @@ func TestGivenLoopingParserDefinition2_ParserPanics(t *testing.T) {
 	})
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("This will end soon") },
-		"Loop detected in parser in git.makaay.nl/mauricem/go-parsekit_test." +
-			"TestGivenLoopingParserDefinition2_ParserPanics.func1 at " +
-			"/home/ubuntu/Projects/Parsekit/go-parsekit/parsehandler_test.go:125"})
+		`Loop detected in parser in .*ParserPanics.* at .*/parsehandler_test.go:\d+`})
+}
+
+func TestGivenNullHandler_HandlePanics(t *testing.T) {
+	parser := parsekit.NewParser(nil)
+	RunPanicTest(t, PanicTest{
+		func() { parser.Execute("") },
+		`ParseAPI.Handle\(\) called with nil input from .*\(\*Parser\).Execute at .*/parsekit\.go:\d+`})
 }
diff --git a/parsekit_test.go b/parsekit_test.go
index 8698693..5f4d210 100644
--- a/parsekit_test.go
+++ b/parsekit_test.go
@@ -4,6 +4,7 @@ package parsekit_test
 // No actual tests belong in this file.
 
 import (
+	"regexp"
 	"testing"
 
 	"git.makaay.nl/mauricem/go-parsekit"
@@ -42,17 +43,17 @@ func RunTokenHandlerTest(t *testing.T, test TokenHandlerTest) {
 
 type PanicTest struct {
 	function func()
-	epxected string
+	expected string
 }
 
 func RunPanicTest(t *testing.T, p PanicTest) {
 	defer func() {
 		if r := recover(); r != nil {
-			if r != p.epxected {
-				t.Errorf("Function did panic, but unexpected panic message received:\nexpected: %q\nactual: %q\n", p.epxected, r)
+			if !regexp.MustCompile(p.expected).MatchString(r.(string)) {
+				t.Errorf("Function did panic, but unexpected panic message received:\nexpected: %q\nactual: %q\n", p.expected, r)
 			}
 		} else {
-			t.Errorf("Function did not panic (expected panic message: %s)", p.epxected)
+			t.Errorf("Function did not panic (expected panic message: %s)", p.expected)
 		}
 	}()
 	p.function()
diff --git a/tokenhandler.go b/tokenhandler.go
index 8089710..ecc1079 100644
--- a/tokenhandler.go
+++ b/tokenhandler.go
@@ -86,7 +86,10 @@ type runeInfo struct {
 // rune is explicitly accepted or skipped as described above.
 func (t *TokenAPI) NextRune() (rune, bool) {
 	if t.currRune != nil {
-		panic("internal Matcher error: NextRune() was called without accepting or skipping the previously read rune")
+		caller, filepos := t.p.getCaller(1)
+		panic(fmt.Sprintf(
+			"TokenHandler bug: NextRune() was called from %s at %s "+
+				"without accepting or skipping the previously read rune", caller, filepos))
 	}
 	r, w, ok := t.p.peek(t.inputOffset)
 	t.currRune = &runeInfo{r, w, ok}
@@ -152,10 +155,16 @@ func (t *TokenAPI) Skip() {
 
 func (t *TokenAPI) checkAllowedCall(name string) {
 	if t.currRune == nil {
-		panic(fmt.Sprintf("internal Matcher error: %s was called without a prior call to NextRune()", name))
+		caller, filepos := t.p.getCaller(2)
+		panic(fmt.Sprintf(
+			"TokenHandler bug: %s was called from %s at %s without a prior call to NextRune()",
+			name, caller, filepos))
 	}
 	if !t.currRune.OK {
-		panic(fmt.Sprintf("internal Matcher error: %s was called, but prior call to NextRune() did not return OK (EOF or invalid rune)", name))
+		caller, filepos := t.p.getCaller(2)
+		panic(fmt.Sprintf(
+			"TokenHandler bug: %s was called from %s at %s, but prior call to NextRune() "+
+				"did not return OK (EOF or invalid rune)", name, caller, filepos))
 	}
 }
 
@@ -169,7 +178,7 @@ func (t *TokenAPI) checkAllowedCall(name string) {
 // input offset which is kept at its current position).
 func (t *TokenAPI) Merge() bool {
 	if t.parent == nil {
-		panic("internal parser error: Cannot call Merge a a non-forked MatchDialog")
+		panic("TokenHandler bug: Cannot call Merge a a non-forked MatchDialog")
 	}
 	t.parent.input = append(t.parent.input, t.input...)
 	t.parent.output = append(t.parent.output, t.output...)
diff --git a/tokenhandler_test.go b/tokenhandler_test.go
index 69fdc45..9e82769 100644
--- a/tokenhandler_test.go
+++ b/tokenhandler_test.go
@@ -30,7 +30,8 @@ func TestGivenNextRuneCalled_WithoutAcceptOrSkip_NextCallToNextRunePanics(t *tes
 	}, "test")
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("input string") },
-		"internal Matcher error: NextRune() was called without accepting or skipping the previously read rune"})
+		`TokenHandler bug: NextRune\(\) was called from .*NextCallToNextRunePanics.* ` +
+			`at .*/tokenhandler_test\.go:\d+ without accepting or skipping the previously read rune`})
 }
 
 func TestGivenNextRuneNotCalled_CallToAcceptPanics(t *testing.T) {
@@ -40,7 +41,8 @@ func TestGivenNextRuneNotCalled_CallToAcceptPanics(t *testing.T) {
 	}, "test")
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("input string") },
-		"internal Matcher error: Accept() was called without a prior call to NextRune()"})
+		`TokenHandler bug: Accept\(\) was called from .*CallToAcceptPanics.* ` +
+			`at .*/tokenhandler_test\.go:\d+ without a prior call to NextRune\(\)`})
 }
 
 func TestGivenNextRuneNotCalled_CallToSkipPanics(t *testing.T) {
@@ -50,7 +52,8 @@ func TestGivenNextRuneNotCalled_CallToSkipPanics(t *testing.T) {
 	}, "test")
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("input string") },
-		"internal Matcher error: Skip() was called without a prior call to NextRune()"})
+		`TokenHandler bug: Skip\(\) was called from .*CallToSkipPanics.* ` +
+			`at .*tokenhandler_test\.go:\d+ without a prior call to NextRune\(\)`})
 }
 
 func TestGivenNextRuneReturningNotOk_CallToAcceptPanics(t *testing.T) {
@@ -61,7 +64,9 @@ func TestGivenNextRuneReturningNotOk_CallToAcceptPanics(t *testing.T) {
 	}, "test")
 	RunPanicTest(t, PanicTest{
 		func() { parser.Execute("\xcd") },
-		"internal Matcher error: Accept() was called, but prior call to NextRune() did not return OK (EOF or invalid rune)"})
+		`TokenHandler bug: Accept\(\) was called from .*CallToAcceptPanics.* ` +
+			`at .*tokenhandler_test\.go:\d+, but prior call to NextRune\(\) did not ` +
+			`return OK \(EOF or invalid rune\)`})
 }
 
 func TestGivenRootTokenAPI_CallingMergePanics(t *testing.T) {
@@ -70,6 +75,6 @@ func TestGivenRootTokenAPI_CallingMergePanics(t *testing.T) {
 			a := parsekit.TokenAPI{}
 			a.Merge()
 		},
-		"internal parser error: Cannot call Merge a a non-forked MatchDialog",
+		`TokenHandler bug: Cannot call Merge a a non-forked MatchDialog`,
 	})
 }
diff --git a/tokenhandlers_builtin.go b/tokenhandlers_builtin.go
index 0c72634..ecbe8c8 100644
--- a/tokenhandlers_builtin.go
+++ b/tokenhandlers_builtin.go
@@ -94,7 +94,7 @@ func MatchRunes(expected ...rune) TokenHandler {
 // creates a TokenHandler that will match any of 'g', 'h', 'i', 'j' or 'k'.
 func MatchRuneRange(start rune, end rune) TokenHandler {
 	if end < start {
-		panic(fmt.Sprintf("internal parser error: MatchRuneRange definition error: start %q must not be < end %q", start, end))
+		panic(fmt.Sprintf("TokenHandler bug: MatchRuneRange definition error: start %q must not be < end %q", start, end))
 	}
 	return func(t *TokenAPI) bool {
 		input, ok := t.NextRune()
@@ -210,7 +210,7 @@ func MatchRep(times int, handler TokenHandler) TokenHandler {
 // When more matches are possible, these will be included in the output.
 func MatchMin(min int, handler TokenHandler) TokenHandler {
 	if min < 0 {
-		panic("internal parser error: MatchMin definition error: min must be >= 0")
+		panic("TokenHandler bug: MatchMin definition error: min must be >= 0")
 	}
 	return matchMinMax(min, -1, handler, "MatchMin")
 }
@@ -221,7 +221,7 @@ func MatchMin(min int, handler TokenHandler) TokenHandler {
 // Zero matches are considered a successful match.
 func MatchMax(max int, handler TokenHandler) TokenHandler {
 	if max < 0 {
-		panic("internal parser error: MatchMax definition error: max must be >= 0")
+		panic("TokenHandler bug: MatchMax definition error: max must be >= 0")
 	}
 	return matchMinMax(0, max, handler, "MatchMax")
 }
@@ -244,17 +244,17 @@ func MatchOneOrMore(handler TokenHandler) TokenHandler {
 // inclusive. All matches will be included in the output.
 func MatchMinMax(min int, max int, handler TokenHandler) TokenHandler {
 	if max < 0 {
-		panic("internal parser error: MatchMinMax definition error: max must be >= 0")
+		panic("TokenHandler bug: MatchMinMax definition error: max must be >= 0")
 	}
 	if min < 0 {
-		panic("internal parser error: MatchMinMax definition error: min must be >= 0")
+		panic("TokenHandler bug: MatchMinMax definition error: min must be >= 0")
 	}
 	return matchMinMax(min, max, handler, "MatchMinMax")
 }
 
 func matchMinMax(min int, max int, handler TokenHandler, name string) TokenHandler {
 	if max >= 0 && min > max {
-		panic(fmt.Sprintf("internal parser error: %s definition error: max %d must not be < min %d", name, max, min))
+		panic(fmt.Sprintf("TokenHandler bug: %s definition error: max %d must not be < min %d", name, max, min))
 	}
 	return func(t *TokenAPI) bool {
 		child := t.Fork()
diff --git a/tokenhandlers_builtin_test.go b/tokenhandlers_builtin_test.go
index e716df1..4fc6cf6 100644
--- a/tokenhandlers_builtin_test.go
+++ b/tokenhandlers_builtin_test.go
@@ -84,17 +84,17 @@ func TestCombinators(t *testing.T) {
 func TestCombinatorPanics(t *testing.T) {
 	RunPanicTests(t, []PanicTest{
 		{func() { parsekit.C.RuneRange('z', 'a') },
-			"internal parser error: MatchRuneRange definition error: start 'z' must not be < end 'a'"},
+			"TokenHandler bug: MatchRuneRange definition error: start 'z' must not be < end 'a'"},
 		{func() { parsekit.C.MinMax(-1, 1, parsekit.A.Space) },
-			"internal parser error: MatchMinMax definition error: min must be >= 0"},
+			"TokenHandler bug: MatchMinMax definition error: min must be >= 0"},
 		{func() { parsekit.C.MinMax(1, -1, parsekit.A.Space) },
-			"internal parser error: MatchMinMax definition error: max must be >= 0"},
+			"TokenHandler bug: MatchMinMax definition error: max must be >= 0"},
 		{func() { parsekit.C.MinMax(10, 5, parsekit.A.Space) },
-			"internal parser error: MatchMinMax definition error: max 5 must not be < min 10"},
+			"TokenHandler bug: MatchMinMax definition error: max 5 must not be < min 10"},
 		{func() { parsekit.C.Min(-10, parsekit.A.Space) },
-			"internal parser error: MatchMin definition error: min must be >= 0"},
+			"TokenHandler bug: MatchMin definition error: min must be >= 0"},
 		{func() { parsekit.C.Max(-42, parsekit.A.Space) },
-			"internal parser error: MatchMax definition error: max must be >= 0"},
+			"TokenHandler bug: MatchMax definition error: max must be >= 0"},
 	})
 }