diff --git a/libretro-common/include/streams/file_stream.h b/libretro-common/include/streams/file_stream.h
index ab198b28eb..2bafc36b61 100644
--- a/libretro-common/include/streams/file_stream.h
+++ b/libretro-common/include/streams/file_stream.h
@@ -81,7 +81,7 @@ char* filestream_gets(RFILE *stream, char *s, size_t len);
 
 int filestream_getc(RFILE *stream);
 
-int filestream_scanf(RFILE *stream, const char* format, ...);
+int filestream_vscanf(RFILE *stream, const char* format, va_list *args);
 
 int filestream_eof(RFILE *stream);
 
diff --git a/libretro-common/streams/file_stream.c b/libretro-common/streams/file_stream.c
index c43423771c..b9def6f942 100644
--- a/libretro-common/streams/file_stream.c
+++ b/libretro-common/streams/file_stream.c
@@ -221,11 +221,11 @@ int filestream_getc(RFILE *stream)
    return EOF;
 }
 
-int filestream_scanf(RFILE *stream, const char* format, ...)
+int filestream_vscanf(RFILE *stream, const char* format, va_list *args)
 {
    char buf[4096];
    char subfmt[64];
-   va_list args;
+   va_list args_copy;
    const char * bufiter = buf;
    int        ret       = 0;
    int64_t startpos     = filestream_tell(stream);
@@ -236,7 +236,12 @@ int filestream_scanf(RFILE *stream, const char* format, ...)
 
    buf[maxlen] = '\0';
 
-   va_start(args, format);
+   /* Have to copy the input va_list here
+    * > Calling va_arg() on 'args' directly would
+    *   cause the va_list to have an indeterminate value
+    *   in the function calling filestream_vscanf(),
+    *   leading to unexpected behaviour */
+   va_copy(args_copy, *args);
 
    while (*format)
    {
@@ -302,7 +307,7 @@ int filestream_scanf(RFILE *stream, const char* format, ...)
          }
          else
          {
-            int v = sscanf(bufiter, subfmt, va_arg(args, void*), &sublen);
+            int v = sscanf(bufiter, subfmt, va_arg(args_copy, void*), &sublen);
             if (v == EOF)
                return EOF;
             if (v != 1)
@@ -327,7 +332,7 @@ int filestream_scanf(RFILE *stream, const char* format, ...)
       }
    }
 
-   va_end(args);
+   va_end(args_copy);
    filestream_seek(stream, startpos+(bufiter-buf),
          RETRO_VFS_SEEK_POSITION_START);
 
diff --git a/libretro-common/streams/file_stream_transforms.c b/libretro-common/streams/file_stream_transforms.c
index 099b27b489..cc6965f7b1 100644
--- a/libretro-common/streams/file_stream_transforms.c
+++ b/libretro-common/streams/file_stream_transforms.c
@@ -153,7 +153,7 @@ int rfscanf(RFILE * stream, const char * format, ...)
    int result;
    va_list vl;
    va_start(vl, format);
-   result = filestream_scanf(stream, format, vl);
+   result = filestream_vscanf(stream, format, &vl);
    va_end(vl);
    return result;
 }