diff --git a/src/journal/compress.c b/src/journal/compress.c
index 626e079fef..a59c2b7a88 100644
--- a/src/journal/compress.c
+++ b/src/journal/compress.c
@@ -458,9 +458,6 @@ int decompress_startswith_zstd(
                 const void *prefix, size_t prefix_len,
                 uint8_t extra) {
 #if HAVE_ZSTD
-        _cleanup_(ZSTD_freeDCtxp) ZSTD_DCtx *dctx = NULL;
-        size_t k;
-
         assert(src);
         assert(src_size > 0);
         assert(buffer);
@@ -468,7 +465,14 @@ int decompress_startswith_zstd(
         assert(prefix);
         assert(*buffer_size == 0 || *buffer);
 
-        dctx = ZSTD_createDCtx();
+        uint64_t size = ZSTD_getFrameContentSize(src, src_size);
+        if (IN_SET(size, ZSTD_CONTENTSIZE_ERROR, ZSTD_CONTENTSIZE_UNKNOWN))
+                return -EBADMSG;
+
+        if (size < prefix_len + 1)
+                return 0; /* Decompressed text too short to match the prefix and extra */
+
+        _cleanup_(ZSTD_freeDCtxp) ZSTD_DCtx *dctx = ZSTD_createDCtx();
         if (!dctx)
                 return -ENOMEM;
 
@@ -483,30 +487,17 @@ int decompress_startswith_zstd(
                 .dst = *buffer,
                 .size = *buffer_size,
         };
+        size_t k;
 
-        for (;;) {
-                k = ZSTD_decompressStream(dctx, &output, &input);
-                if (ZSTD_isError(k)) {
-                        log_debug("ZSTD decoder failed: %s", ZSTD_getErrorName(k));
-                        return zstd_ret_to_errno(k);
-                }
-
-                if (output.pos >= prefix_len + 1)
-                        return memcmp(*buffer, prefix, prefix_len) == 0 &&
-                                      ((const uint8_t*) *buffer)[prefix_len] == extra;
-
-                if (input.pos >= input.size)
-                        return 0;
-
-                if (*buffer_size > SIZE_MAX/2)
-                        return -ENOBUFS;
-
-                if (!(greedy_realloc(buffer, buffer_size, *buffer_size * 2, 1)))
-                        return -ENOMEM;
-
-                output.dst = *buffer;
-                output.size = *buffer_size;
+        k = ZSTD_decompressStream(dctx, &output, &input);
+        if (ZSTD_isError(k)) {
+                log_debug("ZSTD decoder failed: %s", ZSTD_getErrorName(k));
+                return zstd_ret_to_errno(k);
         }
+        assert(output.pos >= prefix_len + 1);
+
+        return memcmp(*buffer, prefix, prefix_len) == 0 &&
+                ((const uint8_t*) *buffer)[prefix_len] == extra;
 #else
         return -EPROTONOSUPPORT;
 #endif
diff --git a/src/journal/test-compress.c b/src/journal/test-compress.c
index 0990f7604d..f50fb0acea 100644
--- a/src/journal/test-compress.c
+++ b/src/journal/test-compress.c
@@ -232,6 +232,8 @@ static void test_lz4_decompress_partial(void) {
         int r;
         _cleanup_free_ char *huge = NULL;
 
+        log_debug("/* %s */", __func__);
+
         assert_se(huge = malloc(HUGE_SIZE));
         memcpy(huge, "HUGE=", STRLEN("HUGE="));
         memset(&huge[STRLEN("HUGE=")], 'x', HUGE_SIZE - STRLEN("HUGE=") - 1);