diff --git a/grammars/c/c_test.go b/grammars/c/c_test.go
index a5a8422..7965ad1 100644
--- a/grammars/c/c_test.go
+++ b/grammars/c/c_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline c.peg
+//go:generate go tool peg -strict -switch -inline c.peg
 
 package c
 
diff --git a/grammars/calculator/calculator_test.go b/grammars/calculator/calculator_test.go
index eff4f39..4c4509f 100644
--- a/grammars/calculator/calculator_test.go
+++ b/grammars/calculator/calculator_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline calculator.peg
+//go:generate go tool peg -strict -switch -inline calculator.peg
 
 package calculator
 
diff --git a/grammars/calculatorast/calculator_test.go b/grammars/calculatorast/calculator_test.go
index 0bd3015..55ef10f 100644
--- a/grammars/calculatorast/calculator_test.go
+++ b/grammars/calculatorast/calculator_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline calculator.peg
+//go:generate go tool peg -strict -switch -inline calculator.peg
 
 package calculatorast
 
diff --git a/grammars/fexl/fexl_test.go b/grammars/fexl/fexl_test.go
index 7c226c4..e8ab8ad 100644
--- a/grammars/fexl/fexl_test.go
+++ b/grammars/fexl/fexl_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline fexl.peg
+//go:generate go tool peg -strict -switch -inline fexl.peg
 
 package fexl
 
diff --git a/grammars/java/java_test.go b/grammars/java/java_test.go
index 20d7838..a0e692a 100644
--- a/grammars/java/java_test.go
+++ b/grammars/java/java_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline java_1_7.peg
+//go:generate go tool peg -strict -switch -inline java_1_7.peg
 
 package java
 
diff --git a/grammars/longtest/long_test.go b/grammars/longtest/long_test.go
index 506656e..dd6f7a2 100644
--- a/grammars/longtest/long_test.go
+++ b/grammars/longtest/long_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go tool peg -switch -inline long.peg
+//go:generate go tool peg -strict -switch -inline long.peg
 
 package longtest