diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index aa383bdb..61296480 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -117,6 +117,15 @@
 cmake_minimum_required(VERSION 3.10)
 project(perf-tools)
 
+if(WIN32)
+    set(CFLAGS_WARNINGS "/Wall" CACHE STRING "Compiler options for warnings")
+else()
+    set(CFLAGS_WARNINGS "-Wall" CACHE STRING "Compiler options for warnings")
+endif()
+
+set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${CFLAGS_WARNINGS}"
+    CACHE STRING "C compiler options" FORCE)
+
 find_package(Threads)
 link_libraries(${CMAKE_THREAD_LIBS_INIT})
 
diff --git a/source/evp_setpeer.c b/source/evp_setpeer.c
index 58fcf6bb..797049d8 100644
--- a/source/evp_setpeer.c
+++ b/source/evp_setpeer.c
@@ -37,7 +37,6 @@ OSSL_TIME max_time;
 
 void do_setpeer(size_t num)
 {
-    size_t i;
     OSSL_TIME time;
 
     EVP_PKEY_CTX *pkey_ctx = NULL;
@@ -136,7 +135,6 @@ int main(int argc, char *argv[])
     OSSL_TIME duration;
     int terse = 0;
     int rc = EXIT_FAILURE;
-    size_t i;
     int opt;
 
     char *key = NULL;
@@ -219,8 +217,7 @@ int main(int argc, char *argv[])
         pkey = PEM_read_bio_PrivateKey(pem, NULL, NULL, NULL);
         BIO_free(pem);
         if (pkey == NULL) {
-            fprintf(stderr, "Failed to create key: %llu [%s PEM]\n",
-                    (unsigned long long)i,
+            fprintf(stderr, "Failed to create key: [%s PEM]\n",
                     sample_names[k]);
             return EXIT_FAILURE;
         }
diff --git a/source/newrawkey.c b/source/newrawkey.c
index 176c5bb6..850e5c22 100644
--- a/source/newrawkey.c
+++ b/source/newrawkey.c
@@ -335,7 +335,6 @@ static int threadcount;
 
 void do_newrawkey(size_t num)
 {
-    size_t i;
     EVP_PKEY *pkey;
     OSSL_TIME time;
     const unsigned char *key_data = key_x25519;
diff --git a/source/randbytes.c b/source/randbytes.c
index e923ecd2..7d14fcf6 100644
--- a/source/randbytes.c
+++ b/source/randbytes.c
@@ -34,7 +34,6 @@ static int threadcount;
 
 void do_randbytes(size_t num)
 {
-    size_t i;
     unsigned char buf[32];
     OSSL_TIME time;