diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6ad07d88bed..b7c1e863433 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -165,7 +165,7 @@ endif ()
 if(BUILD_TESTING AND BUILD_SHARED_LIBS OR S2N_FUZZ_TEST)
     target_compile_options(${PROJECT_NAME} PRIVATE -fvisibility=default)
 else()
-    target_compile_options(${PROJECT_NAME} PRIVATE -fvisibility=hidden -DS2N_EXPORTS)
+    target_compile_options(${PROJECT_NAME} PRIVATE -fvisibility=hidden -DS2N_EXPORTS=1)
 endif()
 
 if(S2N_LTO)
@@ -197,7 +197,7 @@ target_compile_options(${PROJECT_NAME} PRIVATE -include "${S2N_PRELUDE}")
 # Match on Release, RelWithDebInfo and MinSizeRel
 # See: https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html#variable:CMAKE_BUILD_TYPE
 if(CMAKE_BUILD_TYPE MATCHES Rel)
-    add_definitions(-DS2N_BUILD_RELEASE)
+    add_definitions(-DS2N_BUILD_RELEASE=1)
 endif()
 
 if(NO_STACK_PROTECTOR)
@@ -316,7 +316,7 @@ function(feature_probe_result PROBE_NAME IS_AVAILABLE)
 
     # define the probe if available
     if(NORMALIZED)
-        add_definitions(-D${PROBE_NAME})
+        add_definitions(-D${PROBE_NAME}=1)
     endif()
 endfunction()
 
@@ -426,7 +426,7 @@ if (S2N_INTERN_LIBCRYPTO)
       DEPENDS libcrypto.symbols
     )
     add_dependencies(${PROJECT_NAME} s2n_libcrypto)
-    add_definitions(-DS2N_INTERN_LIBCRYPTO)
+    add_definitions(-DS2N_INTERN_LIBCRYPTO=1)
 
     if ((BUILD_SHARED_LIBS AND BUILD_TESTING) OR NOT BUILD_SHARED_LIBS)
         # if libcrypto needs to be interned, rewrite libcrypto references so use of internal functions will link correctly
diff --git a/codebuild/bin/grep_simple_mistakes.sh b/codebuild/bin/grep_simple_mistakes.sh
index ad9806ec2d7..2f2b9d29da1 100755
--- a/codebuild/bin/grep_simple_mistakes.sh
+++ b/codebuild/bin/grep_simple_mistakes.sh
@@ -14,6 +14,20 @@
 
 FAILED=0
 
+#############################################
+# Grep for command line defines without values
+#############################################
+EMPTY_DEFINES=$(grep -Eon "\-D[^=]+=?" CMakeLists.txt | grep -v =)
+if [ ! -z "${EMPTY_DEFINES}" ]; then
+    FAILED=1
+    printf "\e[1;34mCommand line define is missing value:\e[0m "
+    printf "Compilers SHOULD set a default value of 1 when no default is given, "
+    printf "but that behavior is not required by any official spec. Set a value just in case. "
+    printf "For example: -DS2N_FOO=1 instead of -DS2N_FOO.\n"
+    printf "Found: \n"
+    echo "$EMPTY_DEFINES"
+fi
+
 #############################################
 # Grep for bindings methods without C documentation links.
 #############################################
diff --git a/s2n.mk b/s2n.mk
index efc42f49920..b48a876eff8 100644
--- a/s2n.mk
+++ b/s2n.mk
@@ -134,7 +134,7 @@ bindir ?= $(exec_prefix)/bin
 libdir ?= $(exec_prefix)/lib64
 includedir ?= $(exec_prefix)/include
 
-feature_probe = $(shell $(CC) $(CFLAGS) $(shell cat $(S2N_ROOT)/tests/features/GLOBAL.flags) $(shell cat $(S2N_ROOT)/tests/features/$(1).flags) -c -o tmp.o $(S2N_ROOT)/tests/features/$(1).c > /dev/null 2>&1 && echo "-D$(1)"; rm tmp.o > /dev/null 2>&1)
+feature_probe = $(shell $(CC) $(CFLAGS) $(shell cat $(S2N_ROOT)/tests/features/GLOBAL.flags) $(shell cat $(S2N_ROOT)/tests/features/$(1).flags) -c -o tmp.o $(S2N_ROOT)/tests/features/$(1).c > /dev/null 2>&1 && echo "-D$(1)=1"; rm tmp.o > /dev/null 2>&1)
 
 FEATURES := $(notdir $(patsubst %.c,%,$(wildcard $(S2N_ROOT)/tests/features/*.c)))
 SUPPORTED_FEATURES := $(foreach feature,$(FEATURES),$(call feature_probe,$(feature)))