diff --git a/qemu-img.c b/qemu-img.c
index ea62d2d61e..62b29e7feb 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -3381,7 +3381,7 @@ static int img_resize(int argc, char **argv)
     Error *err = NULL;
     int c, ret, relative;
     const char *filename, *fmt, *size;
-    int64_t n, total_size, current_size;
+    int64_t n, total_size, current_size, new_size;
     bool quiet = false;
     BlockBackend *blk = NULL;
     PreallocMode prealloc = PREALLOC_MODE_OFF;
@@ -3557,11 +3557,42 @@ static int img_resize(int argc, char **argv)
     }
 
     ret = blk_truncate(blk, total_size, prealloc, &err);
-    if (!ret) {
-        qprintf(quiet, "Image resized.\n");
-    } else {
+    if (ret < 0) {
         error_report_err(err);
+        goto out;
     }
+
+    new_size = blk_getlength(blk);
+    if (new_size < 0) {
+        error_report("Failed to verify truncated image length: %s",
+                     strerror(-new_size));
+        ret = -1;
+        goto out;
+    }
+
+    /* Some block drivers implement a truncation method, but only so
+     * the user can cause qemu to refresh the image's size from disk.
+     * The idea is that the user resizes the image outside of qemu and
+     * then invokes block_resize to inform qemu about it.
+     * (This includes iscsi and file-posix for device files.)
+     * Of course, that is not the behavior someone invoking
+     * qemu-img resize would find useful, so we catch that behavior
+     * here and tell the user. */
+    if (new_size != total_size && new_size == current_size) {
+        error_report("Image was not resized; resizing may not be supported "
+                     "for this image");
+        ret = -1;
+        goto out;
+    }
+
+    if (new_size != total_size) {
+        warn_report("Image should have been resized to %" PRIi64
+                    " bytes, but was resized to %" PRIi64 " bytes",
+                    total_size, new_size);
+    }
+
+    qprintf(quiet, "Image resized.\n");
+
 out:
     blk_unref(blk);
     if (ret) {