diff --git a/src/FFI.php b/src/FFI.php
index f259f7b..ff7d689 100644
--- a/src/FFI.php
+++ b/src/FFI.php
@@ -539,6 +539,8 @@ private static function init(): void
 typedef void (*FreeFn)(void* a);
 void vips_value_set_blob (GValue* value,
     FreeFn free_fn, void* data, size_t length);
+void* vips_blob_copy (const void *data, size_t length);
+void vips_area_unref (void *area);
 
 const char* vips_value_get_ref_string (const GValue* value,
     size_t* length);
@@ -760,8 +762,7 @@ private static function init(): void
 
 VipsSource* vips_source_new_from_descriptor (int descriptor);
 VipsSource* vips_source_new_from_file (const char* filename);
-VipsSource* vips_source_new_from_memory (const void* data,
-    size_t size);
+VipsSource* vips_source_new_from_blob (void* blob);
 
 typedef struct _VipsSourceCustom {
     VipsSource parent_object;
diff --git a/src/Source.php b/src/Source.php
index 9a028a7..5afdbb0 100644
--- a/src/Source.php
+++ b/src/Source.php
@@ -64,17 +64,19 @@ public static function newFromFile(string $filename): self
      */
     public static function newFromMemory(string $data): self
     {
-        # we need to set the memory to a copy of the data that vips_lib
-        # can own and free
-        $n = strlen($data);
-        $memory = FFI::vips()->new("char[$n]", false, true);
-        \FFI::memcpy($memory, $data, $n);
-        $pointer = FFI::vips()->vips_source_new_from_memory($memory, $n);
+        $blob = FFI::vips()->vips_blob_copy($data, strlen($data));
+        if ($blob === null) {
+            throw new Exception("can't create source from memory");
+        }
 
+        $pointer = FFI::vips()->vips_source_new_from_blob($blob);
         if ($pointer === null) {
+            FFI::vips()->vips_area_unref($blob);
             throw new Exception("can't create source from memory");
         }
 
-        return new self($pointer);
+        $source = new self($pointer);
+        FFI::vips()->vips_area_unref($blob);
+        return $source;
     }
 }