diff --git a/core/constant_inc.php b/core/constant_inc.php
index 91bcabc038..a1deb94ea4 100644
--- a/core/constant_inc.php
+++ b/core/constant_inc.php
@@ -259,6 +259,7 @@
 define( 'ERROR_SPAM_SUSPECTED', 27 );
 define( 'ERROR_FIELD_TOO_LONG', 28 );
 define( 'ERROR_INVALID_FIELD_VALUE', 29 );
+define( 'ERROR_LOGFILE_NOT_WRITABLE', 30 );
 
 # ERROR_CONFIG_*
 define( 'ERROR_CONFIG_OPT_NOT_FOUND', 100 );
diff --git a/core/logging_api.php b/core/logging_api.php
index c5736d51a6..73c0d5a577 100644
--- a/core/logging_api.php
+++ b/core/logging_api.php
@@ -106,7 +106,26 @@ function log_event( $p_level, $p_msg ) {
 		case 'none':
 			break;
 		case 'file':
-			error_log( $t_php_event . PHP_EOL, 3, $t_modifiers );
+			if( isset( $t_modifiers ) ) {
+				# Detect if the log file is writable; if not, issue a one-time warning
+				static $s_log_writable = null;
+				if( $s_log_writable === null ) {
+					$s_log_writable = is_writable( $t_modifiers );
+					if( !$s_log_writable ) {
+						# Display warning message and write it in PHP system log as well.
+						# Note: to ensure the error is shown regardless of $g_display_error settings,
+						# we manually set the message and log it with error_log_delayed(), which will
+						# cause it to be displayed at page bottom.
+						error_parameters( $t_modifiers );
+						$t_message = error_string( ERROR_LOGFILE_NOT_WRITABLE );
+						error_log_delayed( $t_message );
+						error_log( 'MantisBT - ' . htmlspecialchars_decode( $t_message ) );
+					}
+				}
+				if( $s_log_writable ) {
+					error_log( $t_php_event . PHP_EOL, 3, $t_modifiers );
+				}
+			}
 			break;
 		case 'page':
 			global $g_log_events;
diff --git a/lang/strings_english.txt b/lang/strings_english.txt
index c22c19ca8f..efb258f2a8 100644
--- a/lang/strings_english.txt
+++ b/lang/strings_english.txt
@@ -1770,6 +1770,7 @@ $MANTIS_ERROR[ERROR_BUG_CONFLICTING_EDIT] = 'This issue has been updated by anot
 $MANTIS_ERROR[ERROR_SPAM_SUSPECTED] = 'You have reached the allowed activity limit of %d events within the last %d seconds; your action has been blocked to avoid spam, please try again later.';
 $MANTIS_ERROR[ERROR_FIELD_TOO_LONG] = 'Field "%1$s" must be shorter or equal to %2$d characters long.';
 $MANTIS_ERROR[ERROR_API_TOKEN_NAME_NOT_UNIQUE] = 'API token name "%s" is already being used. Please go back and select another one.';
+$MANTIS_ERROR[ERROR_LOGFILE_NOT_WRITABLE] = 'The file specified in $g_log_destination "%s" is not writable.';
 
 # dropzone.js - placeholders format is defined by the library
 $s_dropzone_default_message = 'Drop files here to upload (or click)';