diff --git a/modules/modperl/CMakeLists.txt b/modules/modperl/CMakeLists.txt
index f08401a6..58ee9016 100644
--- a/modules/modperl/CMakeLists.txt
+++ b/modules/modperl/CMakeLists.txt
@@ -34,7 +34,8 @@ if(SWIG_FOUND)
 		"${CMAKE_CURRENT_SOURCE_DIR}/codegen.pl"
 		"${CMAKE_CURRENT_SOURCE_DIR}/functions.in"
 		"perlfunctions.cpp"
-		VERBATIM)
+		VERBATIM
+		DEPENDS codegen.pl functions.in)
 
 	add_custom_command(
 		OUTPUT swigperlrun.h
diff --git a/modules/modpython/CMakeLists.txt b/modules/modpython/CMakeLists.txt
index 279fe491..0ba7a6c8 100644
--- a/modules/modpython/CMakeLists.txt
+++ b/modules/modpython/CMakeLists.txt
@@ -31,7 +31,9 @@ if(SWIG_FOUND)
 		COMMAND "${PERL_EXECUTABLE}"
 		"${CMAKE_CURRENT_SOURCE_DIR}/codegen.pl"
 		"${CMAKE_CURRENT_SOURCE_DIR}/functions.in"
-		"pyfunctions.cpp")
+		"pyfunctions.cpp"
+		VERBATIM
+		DEPENDS codegen.pl functions.in)
 
 	add_custom_command(
 		OUTPUT "swigpyrun.h"