diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index a6110961..80c499c8 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -52,6 +52,24 @@ jobs:
         test/health.awk < log > json
         scp -o "StrictHostKeyChecking=no" json "root@176.9.217.245:/data/downloads/health/linux_${{ matrix.target }}_${{ matrix.cc }}_${{ matrix.ssl }}_${{ matrix.select }}_$(date +"%Y%m%d").json"
 
+  c89:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target: [diabish, ppc_diabish]
+        ssl: ["", BUILTIN]
+    name: C89 ${{ matrix.target }} SSL=${{ matrix.ssl }}
+    env:
+      SSL: ${{ matrix.ssl }}
+      TFLAGS: -DMG_ENABLE_POLL=0 -DMG_ENABLE_EPOLL=0 -DMG_ENABLE_CHACHA20=0 -DMQTT_LOCALHOST -DNO_ZU_TEST
+    steps:
+    - uses: actions/checkout@v5
+      with: { fetch-depth: 2 }
+    - run: | # GH runners seem to overflow the 32-bit FS for the QEMU PPC (works for me in RHEL9)
+        if [[ "${{ matrix.target }}" = ppc_* ]]; then export TFLAGS="$TFLAGS -D_FILE_OFFSET_BITS=64"; fi
+        sudo apt -y update ; sudo apt -y install binfmt-support qemu-user-static && ./test/setup_mqtt_server.sh && docker run --rm --privileged multiarch/qemu-user-static --reset -p yes && make -C test ${{ matrix.target }}
+
   mip:
     runs-on: ubuntu-latest
     strategy:
@@ -87,13 +105,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        target: [mip_vc98]
+        target: [mip_vc98, mip_diabish, mip_ppc_diabish]
         ipv6: [0, 1]
     name: MIP C89 ${{ matrix.target }} IPV6=${{ matrix.ipv6 }}
     steps:
     - uses: actions/checkout@v5
       with: { fetch-depth: 2 }
-    - run: make -C test ${{ matrix.target }} IPV6=${{ matrix.ipv6 }}
+    - run: sudo apt -y update ; sudo apt -y install binfmt-support qemu-user-static && docker run --rm --privileged multiarch/qemu-user-static --reset -p yes && make -C test ${{ matrix.target }} IPV6=${{ matrix.ipv6 }}
   mipbe:
     runs-on: ubuntu-latest
     strategy:
diff --git a/mongoose.c b/mongoose.c
index 50a27d18..a3f44d52 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -1014,9 +1014,11 @@ static size_t mg_dash_print_endpoint(mg_pfn_t fn, void *arg, va_list *ap) {
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *set) {
   struct mg_connection *c;
   for (c = mgr->conns; c != NULL; c = c->next) {
-    struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
-    struct mg_dash_user *u = d->u;
+    struct mg_dash_cdata *d;
+    struct mg_dash_user *u;
     if (!c->is_websocket) continue;
+    d = (struct mg_dash_cdata *) c->data;
+    u = d->u;
     if (u == NULL) continue;
     if (set->index != NULL && *set->index < 0) {
       int sz = mg_dash_array_size(set, u);
@@ -8797,7 +8799,7 @@ static void rx_ndp_ra(struct mg_tcpip_if *ifp, struct pkt *pkt) {
   bool gotl2addr = false, gotprefix = false, changed = false;
   uint8_t l2[sizeof(struct mg_l2addr)];
   uint32_t mtu = 0;
-  uint8_t *prefix, prefix_len;
+  uint8_t *prefix = NULL, prefix_len = 0;
 
   if (pkt->pay.len < sizeof(*ra)) return;
   if (ifp->state6 == MG_TCPIP_STATE_UP) {
@@ -18841,7 +18843,7 @@ void mg_tls_ctx_free(struct mg_mgr *mgr) {
 
 
 
-#if MG_TLS == MG_TLS_BUILTIN
+#if MG_TLS == MG_TLS_BUILTIN && MG_ENABLE_CHACHA20
 // ******* BEGIN: chacha-portable/chacha-portable.h ********
 
 #if !defined(__cplusplus) && !defined(_MSC_VER) && \
diff --git a/mongoose.h b/mongoose.h
index 077cdab9..3855e371 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -3363,7 +3363,7 @@ int mg_uecc_generate_random_int(mg_uecc_word_t *random,
 
 
 
-#if MG_TLS == MG_TLS_BUILTIN
+#if MG_TLS == MG_TLS_BUILTIN && MG_ENABLE_CHACHA20
 #ifndef __PORTABLE_8439_H
 #define __PORTABLE_8439_H
 #if defined(__cplusplus)
diff --git a/src/dash.c b/src/dash.c
index 25e5a647..8e47ea29 100644
--- a/src/dash.c
+++ b/src/dash.c
@@ -167,9 +167,11 @@ static size_t mg_dash_print_endpoint(mg_pfn_t fn, void *arg, va_list *ap) {
 void mg_dash_send_change(struct mg_mgr *mgr, struct mg_field_set *set) {
   struct mg_connection *c;
   for (c = mgr->conns; c != NULL; c = c->next) {
-    struct mg_dash_cdata *d = (struct mg_dash_cdata *) c->data;
-    struct mg_dash_user *u = d->u;
+    struct mg_dash_cdata *d;
+    struct mg_dash_user *u;
     if (!c->is_websocket) continue;
+    d = (struct mg_dash_cdata *) c->data;
+    u = d->u;
     if (u == NULL) continue;
     if (set->index != NULL && *set->index < 0) {
       int sz = mg_dash_array_size(set, u);
diff --git a/src/net_builtin.c b/src/net_builtin.c
index 24c3acf1..bca3fbd4 100644
--- a/src/net_builtin.c
+++ b/src/net_builtin.c
@@ -972,7 +972,7 @@ static void rx_ndp_ra(struct mg_tcpip_if *ifp, struct pkt *pkt) {
   bool gotl2addr = false, gotprefix = false, changed = false;
   uint8_t l2[sizeof(struct mg_l2addr)];
   uint32_t mtu = 0;
-  uint8_t *prefix, prefix_len;
+  uint8_t *prefix = NULL, prefix_len = 0;
 
   if (pkt->pay.len < sizeof(*ra)) return;
   if (ifp->state6 == MG_TCPIP_STATE_UP) {
diff --git a/src/tls_chacha20.c b/src/tls_chacha20.c
index bf03d01e..c69516fe 100644
--- a/src/tls_chacha20.c
+++ b/src/tls_chacha20.c
@@ -7,7 +7,7 @@
 #include "tls_chacha20.h"
 #include "tls.h"
 
-#if MG_TLS == MG_TLS_BUILTIN
+#if MG_TLS == MG_TLS_BUILTIN && MG_ENABLE_CHACHA20
 // ******* BEGIN: chacha-portable/chacha-portable.h ********
 
 #if !defined(__cplusplus) && !defined(_MSC_VER) && \
diff --git a/src/tls_chacha20.h b/src/tls_chacha20.h
index 733d0404..2571d0d2 100644
--- a/src/tls_chacha20.h
+++ b/src/tls_chacha20.h
@@ -8,7 +8,7 @@
 #include "config.h"
 #include "tls.h"
 
-#if MG_TLS == MG_TLS_BUILTIN
+#if MG_TLS == MG_TLS_BUILTIN && MG_ENABLE_CHACHA20
 #ifndef __PORTABLE_8439_H
 #define __PORTABLE_8439_H
 #if defined(__cplusplus)
diff --git a/test/Makefile b/test/Makefile
index e9f0f136..5d4aa0f5 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -248,6 +248,26 @@ mip_port_s390: CC = $(DOCKER) mdashnet/s390 cc
 mip_port_s390: RUN = $(DOCKER) --init mdashnet/s390
 mip_port_s390: mip_port_test
 
+diabish: CC = gcc
+diabish: CFLAGS += -std=gnu89 -Werror=declaration-after-statement -Werror=vla -Wno-pedantic
+diabish: test
+
+mip_diabish: CC = gcc
+mip_diabish: CFLAGS += -std=gnu89 -Werror=declaration-after-statement -Werror=vla -Wno-pedantic
+mip_diabish: mip_test
+
+ppc_diabish: ASAN=
+ppc_diabish: CFLAGS += -std=gnu89 -Werror=declaration-after-statement -Werror=vla -Wno-pedantic
+ppc_diabish: CC = $(DOCKER) dockcross/linux-ppc powerpc-unknown-linux-gnu-gcc -static
+ppc_diabish: RUN = qemu-ppc-static
+ppc_diabish: test
+
+mip_ppc_diabish: ASAN=
+mip_ppc_diabish: CFLAGS += -std=gnu89 -Werror=declaration-after-statement -Werror=vla -Wno-pedantic
+mip_ppc_diabish: CC = $(DOCKER) dockcross/linux-ppc powerpc-unknown-linux-gnu-gcc -static
+mip_ppc_diabish: RUN = qemu-ppc-static
+mip_ppc_diabish: mip_test
+
 arm: DEFS += -DMG_ENABLE_POSIX_FS=0 -DMG_ENABLE_TCPIP=1 -DMG_ENABLE_TCPIP_DRIVER_INIT=0 -DMG_ARCH=MG_ARCH_ARMGCC -DNO_SLEEP_ABORT
 arm: mongoose.h $(SRCS) mip_test.c
 	$(DOCKER) mdashnet/armgcc arm-none-eabi-gcc -mcpu=cortex-m3 -mthumb $(SRCS) $(OPTS) $(WARN) $(INCS) $(DEFS) $(TFLAGS) -o unit_test -nostartfiles --specs nosys.specs -e 0
diff --git a/test/unit_test.c b/test/unit_test.c
index b632ec83..e08c75a6 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -339,7 +339,7 @@ static void sntp_cb(struct mg_connection *c, int ev, void *ev_data) {
     int64_t received = *(int64_t *) ev_data;
     *(int64_t *) c->fn_data = received;
     MG_DEBUG(("got time: %lld", received));
-#if MG_ARCH == MG_ARCH_UNIX
+#if MG_ARCH == MG_ARCH_UNIX && defined(__STDC__) && defined(__STDC_VERSION__)
     struct timeval tv = {0, 0};
     gettimeofday(&tv, 0);
     int64_t ms = (int64_t) tv.tv_sec * 1000 + tv.tv_usec / 1000;
@@ -1462,7 +1462,7 @@ static void test_tls(void) {
   const char *url = "https://localhost:12347";
   char buf[FETCH_BUF_SIZE];
   struct mg_tls_opts opts;
-  struct mg_str data = mg_unpacked("/Makefile");
+  struct mg_str data = mg_unpacked("/fuzz.c");
   char bigdata[FETCH_BUF_SIZE - 256];  // leave extra room
   struct mg_str bd;
   ASSERT(data.buf != NULL && data.len > 0);
@@ -1505,6 +1505,7 @@ static void test_tls(void) {
     // otherwise it will end with 200 and shorter file contents
     ASSERT(fetch(&mgr, buf, "https://localhost:8443",
                  "GET /thefile HTTP/1.0\n\n") == 200);
+    data = mg_unpacked("/Makefile");
     ASSERT(cmpbody(buf, data.buf) == 0);  // "thefile" links to Makefile
     ASSERT(system("killall tls_multirec/server") == 0);
   } else {
@@ -3014,7 +3015,7 @@ static void test_util(void) {
 static void test_crc32(void) {
   //  echo -n aaa | cksum -o3
   ASSERT(mg_crc32(0, 0, 0) == 0);
-  ASSERT(mg_crc32(0, "a", 1) == 3904355907);
+  ASSERT(mg_crc32(0, "a", 1) == 3904355907U);
   ASSERT(mg_crc32(0, "abc", 3) == 891568578);
   ASSERT(mg_crc32(mg_crc32(0, "ab", 2), "c", 1) == 891568578);
 }
@@ -4501,7 +4502,7 @@ static bool test_upload_dir(const struct mg_dash_user *u, char *buf, size_t len)
 
 struct test_file_entry {
   char name[64];
-  size_t size;
+  uint64_t size;
 };
 static struct test_file_entry s_test_file;
 static int s_test_file_index;