diff --git a/plugins/gcc10/gcc10-overlay.mk b/plugins/gcc10/gcc10-overlay.mk
index 9cfb9f83..fc55cebd 100644
--- a/plugins/gcc10/gcc10-overlay.mk
+++ b/plugins/gcc10/gcc10-overlay.mk
@@ -33,3 +33,6 @@ db_PATCHES := $(TOP_DIR)/src/db-1-fix-including-winioctl-h-lowcase.patch
 libssh_EXTRA_WARNINGS = -Wno-error=implicit-fallthrough
 gtkimageview_EXTRA_WARNINGS = -Wno-error=misleading-indentation
 guile_EXTRA_WARNINGS = -Wno-error=misleading-indentation
+gtkmm2_EXTRA_WARNINGS = -Wno-error=cast-function-type
+gtkmm3_EXTRA_WARNINGS = -Wno-error=cast-function-type
+gtkglextmm_EXTRA_WARNINGS = -Wno-error=cast-function-type
diff --git a/plugins/gcc9/gcc9-overlay.mk b/plugins/gcc9/gcc9-overlay.mk
index cbdc7ce3..463c8477 100644
--- a/plugins/gcc9/gcc9-overlay.mk
+++ b/plugins/gcc9/gcc9-overlay.mk
@@ -33,3 +33,6 @@ db_PATCHES := $(TOP_DIR)/src/db-1-fix-including-winioctl-h-lowcase.patch
 libssh_EXTRA_WARNINGS = -Wno-error=implicit-fallthrough
 gtkimageview_EXTRA_WARNINGS = -Wno-error=misleading-indentation
 guile_EXTRA_WARNINGS = -Wno-error=misleading-indentation
+gtkmm2_EXTRA_WARNINGS = -Wno-error=cast-function-type
+gtkmm3_EXTRA_WARNINGS = -Wno-error=cast-function-type
+gtkglextmm_EXTRA_WARNINGS = -Wno-error=cast-function-type
diff --git a/src/gtkglextmm.mk b/src/gtkglextmm.mk
index 03b68a5b..caa90754 100644
--- a/src/gtkglextmm.mk
+++ b/src/gtkglextmm.mk
@@ -33,7 +33,7 @@ define $(PKG)_BUILD
     '$(TARGET)-g++' \
         -W -Wall -Werror -Wno-error=deprecated-declarations -pedantic -std=c++0x \
         -Wno-error=deprecated \
-        -Wno-error=cast-function-type \
+        $($(PKG)_EXTRA_WARNINGS) \
         '$(TEST_FILE)' -o '$(PREFIX)/$(TARGET)/bin/test-gtkglextmm.exe' \
         `'$(TARGET)-pkg-config' gtkglextmm-1.2 --cflags --libs`
 endef
diff --git a/src/gtkmm2.mk b/src/gtkmm2.mk
index 59907bd4..9175b2cd 100644
--- a/src/gtkmm2.mk
+++ b/src/gtkmm2.mk
@@ -32,7 +32,7 @@ define $(PKG)_BUILD
     '$(TARGET)-g++' \
         -W -Wall -Wno-deprecated-declarations -Werror -pedantic -std=c++11 \
         -Wno-error=deprecated \
-        -Wno-error=cast-function-type \
+        $($(PKG)_EXTRA_WARNINGS) \
         '$(TEST_FILE)' -o '$(PREFIX)/$(TARGET)/bin/test-gtkmm2.exe' \
         `'$(TARGET)-pkg-config' gtkmm-2.4 --cflags --libs`
 endef
diff --git a/src/gtkmm3.mk b/src/gtkmm3.mk
index 25f5dd3e..fb92410f 100644
--- a/src/gtkmm3.mk
+++ b/src/gtkmm3.mk
@@ -29,7 +29,7 @@ define $(PKG)_BUILD
     '$(TARGET)-g++' \
         -W -Wall -Wno-deprecated-declarations -Werror -pedantic -std=c++11 \
         -Wno-error=deprecated \
-        -Wno-error=cast-function-type \
+        $($(PKG)_EXTRA_WARNINGS) \
         '$(TEST_FILE)' -o '$(PREFIX)/$(TARGET)/bin/test-gtkmm3.exe' \
         `'$(TARGET)-pkg-config' gtkmm-3.0 --cflags --libs`
 endef