diff --git a/src/fix_ave_time.cpp b/src/fix_ave_time.cpp
index ee08c859f4..660d8c155d 100644
--- a/src/fix_ave_time.cpp
+++ b/src/fix_ave_time.cpp
@@ -1009,6 +1009,7 @@ void FixAveTime::options(int iarg, int narg, char **arg)
   noff = 0;
   offlist = nullptr;
   overwrite = 0;
+  yaml_flag = false;
   format_user = nullptr;
   format = (char *) " %g";
   title1 = nullptr;
@@ -1020,11 +1021,12 @@ void FixAveTime::options(int iarg, int narg, char **arg)
   while (iarg < narg) {
     if (strcmp(arg[iarg],"file") == 0) {
       if (iarg+2 > narg) error->all(FLERR,"Illegal fix ave/time command");
+      yaml_flag = utils::strmatch(arg[iarg+1],"\\.[yY][aA]?[mM][lL]$");
       if (me == 0) {
         fp = fopen(arg[iarg+1],"w");
         if (fp == nullptr)
           error->one(FLERR,"Cannot open fix ave/time file {}: {}",
-                                       arg[iarg+1], utils::getsyserror());
+                     arg[iarg+1], utils::getsyserror());
       }
       iarg += 2;
     } else if (strcmp(arg[iarg],"ave") == 0) {
diff --git a/src/fix_ave_time.h b/src/fix_ave_time.h
index d2c7b4752b..dda548b646 100644
--- a/src/fix_ave_time.h
+++ b/src/fix_ave_time.h
@@ -48,6 +48,7 @@ class FixAveTime : public Fix {
   int any_variable_length;
   int all_variable_length;
   int lockforever;
+  bool yaml_flag;
 
   int ave, nwindow, startstep, mode;
   int noff, overwrite;
diff --git a/unittest/utils/test_utils.cpp b/unittest/utils/test_utils.cpp
index 900ce6814c..e452314419 100644
--- a/unittest/utils/test_utils.cpp
+++ b/unittest/utils/test_utils.cpp
@@ -519,6 +519,27 @@ TEST(Utils, strmatch_opt_char)
     ASSERT_FALSE(utils::strmatch("x_name", "^[cfvid]2?_name"));
 }
 
+TEST(Utils, strmatch_yaml_suffix)
+{
+    ASSERT_TRUE(utils::strmatch("test.yaml", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_TRUE(utils::strmatch("test.yml", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_TRUE(utils::strmatch("TEST.YAML", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_TRUE(utils::strmatch("TEST.YML", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("test.yamlx", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("test.ymlx", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("TEST.YAMLX", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("TEST.YMLX", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("testyaml", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("testyml", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("TESTYAML", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("TESTYML", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("yaml.test", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("yml.test", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("YAML.TEST", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("YML.TEST", "\\.[yY][aA]?[mM][lL]$"));
+    ASSERT_FALSE(utils::strmatch("test", "\\.[yY][aA]?[mM][lL]$"));
+}
+
 TEST(Utils, strmatch_dot)
 {
     ASSERT_TRUE(utils::strmatch("rigid", ".igid"));