diff --git a/pkg/u8g2/Makefile.u8g2_csrc b/pkg/u8g2/Makefile.u8g2_csrc
index 8f7452fcc7..04f0eb46c8 100644
--- a/pkg/u8g2/Makefile.u8g2_csrc
+++ b/pkg/u8g2/Makefile.u8g2_csrc
@@ -2,6 +2,9 @@ MODULE = u8g2_csrc
 
 CFLAGS += -Wno-overlength-strings
 
+# avoid compilation errors when NDEBUG is defined
+CFLAGS += -Wno-unused-variable
+
 ifeq (llvm,$(TOOLCHAIN))
   CFLAGS += -Wno-newline-eof
 endif