diff --git a/libtommath/makefile_include.mk b/libtommath/makefile_include.mk
index ceb2d44..711b630 100644
--- a/libtommath/makefile_include.mk
+++ b/libtommath/makefile_include.mk
@@ -50,7 +50,8 @@ endif
 
 LTM_CFLAGS += -I./ -Wall -Wsign-compare -Wextra -Wshadow
 
-ifdef SANITIZER
+# renamed for Dropbear to avoid clash with oss-fuzz $SANITIZER var
+ifdef LTM_SANITIZER
 LTM_CFLAGS += -fsanitize=undefined -fno-sanitize-recover=all -fno-sanitize=float-divide-by-zero
 endif