diff --git a/plugins/Makefile b/plugins/Makefile
index 767a3fa..03ce0de 100644
--- a/plugins/Makefile
+++ b/plugins/Makefile
@@ -1085,6 +1085,9 @@ endif
 # Rack code is not tested for this flag, unset it
 BUILD_CXX_FLAGS += -U_GLIBCXX_ASSERTIONS -Wp,-U_GLIBCXX_ASSERTIONS
 
+# Ignore bad behaviour from Rack API
+BUILD_CXX_FLAGS += -Wno-format-security
+
 ifeq ($(WASM),true)
 BUILD_CXX_FLAGS += -fexceptions
 endif
diff --git a/src/Makefile b/src/Makefile
index a9a0b90..311020c 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -120,6 +120,9 @@ BUILD_CXX_FLAGS += -DnsvgParseFromFile=nsvgParseFromFileCardinal
 # Rack code is not tested for this flag, unset it
 BUILD_CXX_FLAGS += -U_GLIBCXX_ASSERTIONS -Wp,-U_GLIBCXX_ASSERTIONS
 
+# Ignore bad behaviour from Rack API
+BUILD_CXX_FLAGS += -Wno-format-security
+
 # --------------------------------------------------------------
 # Rack files to build
 
diff --git a/src/Makefile.cardinal.mk b/src/Makefile.cardinal.mk
index 70d83dd..45b8dac 100644
--- a/src/Makefile.cardinal.mk
+++ b/src/Makefile.cardinal.mk
@@ -250,6 +250,9 @@ endif
 # Rack code is not tested for this flag, unset it
 BUILD_CXX_FLAGS += -U_GLIBCXX_ASSERTIONS -Wp,-U_GLIBCXX_ASSERTIONS
 
+# Ignore bad behaviour from Rack API
+BUILD_CXX_FLAGS += -Wno-format-security
+
 # --------------------------------------------------------------
 # FIXME lots of warnings from VCV side