diff --git a/common/av_log.c b/common/av_log.c
index d043488979..5599ca0584 100644
--- a/common/av_log.c
+++ b/common/av_log.c
@@ -208,14 +208,36 @@ void print_libav_versions(struct mp_log *log, int v)
 
     mp_msg(log, v, "%s library versions:\n", LIB_PREFIX);
 
+    bool mismatch = false;
+    bool broken = false;
     for (int n = 0; n < MP_ARRAY_SIZE(libs); n++) {
         const struct lib *l = &libs[n];
         mp_msg(log, v, "   %-15s %d.%d.%d", l->name, V(l->buildv));
         if (l->buildv != l->runv) {
             mp_msg(log, v, " (runtime %d.%d.%d)", V(l->runv));
+            mismatch = true;
+            broken |= ((l->buildv & 255) >= 100) != ((l->runv & 255) >= 100);
         }
         mp_msg(log, v, "\n");
     }
+    // This just won't work. It's 100% broken.
+    if (broken) {
+        mp_fatal(log, "mpv was compiled and linked against a mixture of Libav "
+                 "and FFmpeg versions. This won't work and will most likely "
+                 "crash at some point. Exiting.\n");
+        exit(42);
+    }
+    // We don't "really" support mismatched libraries, but if you like to
+    // suffer, you're free to enjoy the terrible aspects of dynamic linking.
+    // In particular, we don't use all these crazy accessors ffmpeg wants us
+    // to use in order to be ABI compatible after Libav merges - because that
+    // would make our code incompatible to Libav. It's madness.
+    if (mismatch) {
+        mp_warn(log, "Warning: mpv was compiled against a different version of "
+                "%s than the shared\nlibrary it is linked against. This can "
+                "expose subtle ABI compatibility issues\nand can lead to "
+                "misbehavior and crashes.\n", LIB_PREFIX);
+    }
 }
 
 #undef V