diff --git a/src/Patchwork/Utf8.php b/src/Patchwork/Utf8.php
index 585f063..4363a08 100644
--- a/src/Patchwork/Utf8.php
+++ b/src/Patchwork/Utf8.php
@@ -235,7 +235,9 @@ public static function strlen($s)
     }
     public static function strpos($s, $needle, $offset = 0)
     {
-        return grapheme_strpos($s, $needle, $offset);
+        // ignore invalid negative offset to keep compatility
+        // with php < 5.5.35, < 5.6.21, < 7.0.6
+        return grapheme_strpos($s, $needle, $offset > 0 ? $offset : 0);
     }
     public static function strrpos($s, $needle, $offset = 0)
     {
diff --git a/tests/PHP/Shim/IntlTest.php b/tests/PHP/Shim/IntlTest.php
index 1d4d4a7..83b3aa8 100644
--- a/tests/PHP/Shim/IntlTest.php
+++ b/tests/PHP/Shim/IntlTest.php
@@ -122,7 +122,7 @@ public function testGrapheme_strpos()
         $this->assertSame(false, grapheme_strpos('abc', ''));
         $this->assertSame(false, grapheme_strpos('abc', 'd'));
         $this->assertSame(false, grapheme_strpos('abc', 'a', 3));
-        $this->assertSame(0, grapheme_strpos('abc', 'a', -1));
+        $this->assertSame(0, grapheme_strpos('abc', 'a', 0));
         $this->assertSame(1, grapheme_strpos('한국어', '국'));
         $this->assertSame(3, grapheme_stripos('DÉJÀ', 'à'));
         $this->assertSame(false, grapheme_strrpos('한국어', ''));
diff --git a/tests/Utf8/HhvmTest.php b/tests/Utf8/HhvmTest.php
index 8a77da0..4eb6866 100644
--- a/tests/Utf8/HhvmTest.php
+++ b/tests/Utf8/HhvmTest.php
@@ -12,7 +12,8 @@ public function test1()
     public function test2()
     {
         // Negative offset are not allowed but native PHP silently casts them to zero
-        $this->assertSame(0, grapheme_strpos('abc', 'a', -1));
+        // Starting with 5.5.35, 5.6.21, 7.0.6, PHP refuse them
+        $this->assertSame(0, grapheme_strpos('abc', 'a', 0));
     }
 
     public function test3()