diff --git a/include/maxscale/modinfo.h b/include/maxscale/modinfo.h
index 4dafa1a68..710638c7e 100644
--- a/include/maxscale/modinfo.h
+++ b/include/maxscale/modinfo.h
@@ -109,6 +109,7 @@ enum mxs_module_param_options
     MXS_MODULE_OPT_PATH_F_OK   = (1 << 4),  /**< PATH: Path must exist */
     MXS_MODULE_OPT_PATH_CREAT  = (1 << 5),  /**< PATH: Create path if it doesn't exist */
     MXS_MODULE_OPT_ENUM_UNIQUE = (1 << 6),  /**< ENUM: Only one value can be defined */
+    MXS_MODULE_OPT_DURATION_S  = (1 << 7),  /**< DURATION: Cannot be specified in milliseconds */
 
     /**< Parameter is deprecated: Causes a warning to be logged if the parameter
      * is used but will not cause a configuration error. */
diff --git a/server/core/config.cc b/server/core/config.cc
index ea9b3d24a..d84e30277 100644
--- a/server/core/config.cc
+++ b/server/core/config.cc
@@ -4484,13 +4484,27 @@ bool config_param_is_valid(const MXS_MODULE_PARAM* params,
                     {
                         valid = true;
 
-                        if (unit == mxs::config::DURATION_IN_DEFAULT)
+                        switch (unit)
                         {
+                        case mxs::config::DURATION_IN_MILLISECONDS:
+                            if (params[i].options & MXS_MODULE_OPT_DURATION_S)
+                            {
+                                MXS_ERROR("Currently the granularity of '%s' is seconds. The value "
+                                          "cannot be specified in milliseconds.", params[i].name);
+                                valid = false;
+                            }
+                            break;
+
+                        case mxs::config::DURATION_IN_DEFAULT:
                             MXS_WARNING("Specifying durations without a suffix denoting the unit "
                                         "has been deprecated: '%s=%s'. Use the suffixes 'h' (hour), "
                                         "'m' (minute) 's' (second) or 'ms' (milliseconds). "
                                         "For instance, '%s=%ss' or '%s=%sms.",
                                         key, value, key, value, key, value);
+                            break;
+
+                        default:
+                            break;
                         }
                     }
                 }
diff --git a/server/core/test/test_config.cc b/server/core/test/test_config.cc
index 206684279..eaf457522 100644
--- a/server/core/test/test_config.cc
+++ b/server/core/test/test_config.cc
@@ -44,6 +44,7 @@ int test_validity()
         {"p7", MXS_MODULE_PARAM_SERVICE,  "my-service"            },
         {"p8", MXS_MODULE_PARAM_ENUM,     "a", MXS_MODULE_OPT_ENUM_UNIQUE, enum_values},
         {"p9", MXS_MODULE_PARAM_DURATION, "4711s"                 },
+        {"p10", MXS_MODULE_PARAM_DURATION, "4711s", MXS_MODULE_OPT_DURATION_S },
         {MXS_END_MODULE_PARAMS}
     };
 
@@ -107,6 +108,7 @@ int test_validity()
     TEST(config_param_is_valid(params, "p9", "4711S", &ctx));
     TEST(config_param_is_valid(params, "p9", "4711MS", &ctx));
     TEST(!config_param_is_valid(params, "p9", "4711q", &ctx));
+    TEST(!config_param_is_valid(params, "p10", "4711ms", &ctx));
 
     /** Service parameter */
     CONFIG_CONTEXT svc("test-service");