diff --git a/plugins/webp-uploads/picture-element.php b/plugins/webp-uploads/picture-element.php
index 349edb3b46..008ecd9d11 100644
--- a/plugins/webp-uploads/picture-element.php
+++ b/plugins/webp-uploads/picture-element.php
@@ -148,6 +148,16 @@ function webp_uploads_wrap_image_in_picture( string $image, string $context, int
 					esc_attr( $image_srcset ),
 					is_string( $sizes ) ? sprintf( ' sizes="%s"', esc_attr( $sizes ) ) : ''
 				);
+			} else {
+				// Fallback when wp_calculate_image_srcset returns false - generate simple source without srcset.
+				$image_url = webp_uploads_get_mime_type_image( $attachment_id, $src, $image_mime_type );
+				if ( is_string( $image_url ) ) {
+					$picture_sources .= sprintf(
+						'<source type="%s" srcset="%s">',
+						esc_attr( $image_mime_type ),
+						esc_attr( $image_url )
+					);
+				}
 			}
 		}
 	} else {
diff --git a/plugins/webp-uploads/tests/test-picture-element.php b/plugins/webp-uploads/tests/test-picture-element.php
index 87ca0282c1..766fd0c981 100644
--- a/plugins/webp-uploads/tests/test-picture-element.php
+++ b/plugins/webp-uploads/tests/test-picture-element.php
@@ -436,10 +436,15 @@ public function test_disable_responsive_image_with_picture_element( Closure $set
 		$this->assertStringEndsWith( '.jpg', $picture_processor->get_attribute( 'src' ), 'Make sure the fallback IMG should return JPEG src.' );
 
 		$picture_processor = new WP_HTML_Tag_Processor( $picture_markup );
+		$source_count      = 0;
 		while ( $picture_processor->next_tag( array( 'tag_name' => 'source' ) ) ) {
+			++$source_count;
 			$this->assertSame( self::$mime_type, $picture_processor->get_attribute( 'type' ), 'Make sure the Picture source should not return JPEG as source.' );
 			$this->assertStringContainsString( '.webp', $picture_processor->get_attribute( 'srcset' ), 'Make sure the Picture source srcset should return WEBP images.' );
 		}
+
+		// Ensure at least one source element was created (addresses GitHub issue with wp_calculate_image_srcset disabled).
+		$this->assertGreaterThan( 0, $source_count, 'At least one source element should be created even when responsive images are disabled.' );
 	}
 
 	/**