diff --git a/src/cairo-pdf-surface.c b/src/cairo-pdf-surface.c
index ddb1bcef3..069fed0dc 100644
--- a/src/cairo-pdf-surface.c
+++ b/src/cairo-pdf-surface.c
@@ -2285,6 +2285,7 @@ static cairo_status_t
 _cairo_pdf_surface_emit_type3_font_subset (cairo_pdf_surface_t		*surface,
 					   cairo_scaled_font_subset_t	*font_subset)
 {
+    cairo_status_t status;
     cairo_pdf_resource_t *glyphs, encoding, char_procs, subset_resource, to_unicode_stream;
     cairo_pdf_font_t font;
     cairo_matrix_t matrix;
@@ -2361,7 +2362,9 @@ _cairo_pdf_surface_emit_type3_font_subset (cairo_pdf_surface_t		*surface,
 
     subset_resource = _cairo_pdf_surface_new_object (surface);
     matrix = font_subset->scaled_font->scale;
-    cairo_matrix_invert (&matrix);
+    status = cairo_matrix_invert (&matrix);
+    /* _cairo_scaled_font_init ensures the matrix is invertible */
+    assert (status == CAIRO_STATUS_SUCCESS);
     _cairo_output_stream_printf (surface->output,
 				 "%d 0 obj\r\n"
 				 "<< /Type /Font\r\n"
diff --git a/src/cairo-ps-surface.c b/src/cairo-ps-surface.c
index 026099649..76d8f450b 100644
--- a/src/cairo-ps-surface.c
+++ b/src/cairo-ps-surface.c
@@ -668,6 +668,7 @@ _cairo_ps_surface_emit_type3_font_subset (cairo_ps_surface_t		*surface,
 
 
 {
+    cairo_status_t status;
     cairo_matrix_t matrix;
     unsigned int i;
 
@@ -680,7 +681,9 @@ _cairo_ps_surface_emit_type3_font_subset (cairo_ps_surface_t		*surface,
 				 font_subset->subset_id);
 
     matrix = font_subset->scaled_font->scale;
-    cairo_matrix_invert (&matrix);
+    status = cairo_matrix_invert (&matrix);
+    /* _cairo_scaled_font_init ensures the matrix is invertible */
+    assert (status == CAIRO_STATUS_SUCCESS);
     _cairo_output_stream_printf (surface->final_stream,
 				 "\t/FontType\t3\n"
 				 "\t/FontMatrix\t[%f %f %f %f 0 0]\n"