diff --git a/crypto_kem/kyber768/clean/api.h b/crypto_kem/kyber768/clean/api.h
index 737a208e..35b6978c 100644
--- a/crypto_kem/kyber768/clean/api.h
+++ b/crypto_kem/kyber768/clean/api.h
@@ -1,5 +1,5 @@
-#ifndef API_H
-#define API_H
+#ifndef PQCLEAN_KYBER768_CLEAN_API_H
+#define PQCLEAN_KYBER768_CLEAN_API_H
 
 #include <stdint.h>
 
diff --git a/crypto_sign/dilithium-iii/clean/api.h b/crypto_sign/dilithium-iii/clean/api.h
index c9c15380..7edbe671 100644
--- a/crypto_sign/dilithium-iii/clean/api.h
+++ b/crypto_sign/dilithium-iii/clean/api.h
@@ -1,6 +1,5 @@
-#ifndef API_H
-#include <stdint.h>
-#define API_H
+#ifndef PQCLEAN_DILITHIUMIII_API_H
+#define PQCLEAN_DILITHIUMIII_API_H
 
 #include <stddef.h>
 #include <stdint.h>
diff --git a/test/Makefile b/test/Makefile
index a21545e3..add8a886 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -15,7 +15,7 @@ COMMON_HEADERS=$(COMMON_DIR)/fips202.h $(COMMON_DIR)/randombytes.h $(COMMON_DIR)
 DEST_DIR=../bin
 
 # This -Wall was supported by the European Commission through the ERC Starting Grant 805031 (EPOQUE)
-CFLAGS=-Wall -Wextra -Wpedantic -Werror -std=c99 -I$(COMMON_DIR) $(EXTRAFLAGS)
+CFLAGS=-Wall -Wextra -Wpedantic -Werror -Wundef -std=c99 -I$(COMMON_DIR) $(EXTRAFLAGS)
 
 all: $(DEST_DIR)/functest_$(SCHEME)_$(IMPLEMENTATION) $(DEST_DIR)/testvectors_$(SCHEME)_$(IMPLEMENTATION)
 
diff --git a/test/crypto_kem/functest.c b/test/crypto_kem/functest.c
index 5a513810..a2721e86 100644
--- a/test/crypto_kem/functest.c
+++ b/test/crypto_kem/functest.c
@@ -50,12 +50,16 @@ static int check_canary(const uint8_t *d) {
         return -1;                                \
     }
 
+#define DEFER(x) x
+#define NAMESPACE_CHECK DEFER(NAMESPACE(API_H))
+
 static int test_keys(void) {
     /*
      * This is most likely going to be aligned by the compiler.
      * 16 extra bytes for canary
      * 1 extra byte for unalignment
      */
+
     uint8_t key_a_aligned[CRYPTO_BYTES + 16 + 1];
     uint8_t key_b_aligned[CRYPTO_BYTES + 16 + 1];
     uint8_t pk_aligned[CRYPTO_PUBLICKEYBYTES + 16 + 1];
@@ -196,7 +200,10 @@ static int test_invalid_ciphertext(void) {
 }
 
 int main(void) {
+    // these two will trigger compiler errors
     puts(CRYPTO_ALGNAME);
+    NAMESPACE_CHECK;
+
     int result = 0;
     result += test_keys();
     result += test_invalid_sk_a();
diff --git a/test/crypto_sign/functest.c b/test/crypto_sign/functest.c
index 11938648..2eaf8f5c 100644
--- a/test/crypto_sign/functest.c
+++ b/test/crypto_sign/functest.c
@@ -51,6 +51,9 @@ static int check_canary(const uint8_t *d) {
         return -1;                                \
     }
 
+#define DEFER(x) x
+#define NAMESPACE_CHECK DEFER(NAMESPACE(API_H))
+
 static int test_sign(void) {
     /*
      * This is most likely going to be aligned by the compiler.
@@ -160,7 +163,10 @@ static int test_wrong_pk(void) {
 }
 
 int main(void) {
+    // these two will generate compile errors
     puts(CRYPTO_ALGNAME);
+    NAMESPACE_CHECK;
+
     int result = 0;
     result += test_sign();
     result += test_wrong_pk();