diff --git a/gnu/packages/photo.scm b/gnu/packages/photo.scm
index 75bbc45380..09767f464e 100644
--- a/gnu/packages/photo.scm
+++ b/gnu/packages/photo.scm
@@ -55,6 +55,7 @@ (define-module (gnu packages photo)
   #:use-module (gnu packages gstreamer)
   #:use-module (gnu packages gtk)
   #:use-module (gnu packages image)
+  #:use-module (gnu packages image-processing)
   #:use-module (gnu packages imagemagick)
   #:use-module (gnu packages iso-codes)
   #:use-module (gnu packages libcanberra)
@@ -63,6 +64,7 @@ (define-module (gnu packages photo)
   #:use-module (gnu packages lua)
   #:use-module (gnu packages man)
   #:use-module (gnu packages maths)
+  #:use-module (gnu packages opencl)
   #:use-module (gnu packages perl)
   #:use-module (gnu packages pkg-config)
   #:use-module (gnu packages popt)
@@ -480,7 +482,13 @@ (define-public darktable
        (modify-phases %standard-phases
          (add-before 'configure 'prepare-build-environment
            (lambda* (#:key inputs #:allow-other-keys)
-             (setenv "CC" "clang") (setenv "CXX" "clang++")))
+             (setenv "CC" "clang") (setenv "CXX" "clang++")
+             ;; Darktable looks for opencl-c.h in the LLVM dir. Guix installs
+             ;; it to the Clang dir. We fix this by patching CMakeLists.txt.
+             (substitute* "CMakeLists.txt"
+               (("\\$\\{LLVM_INSTALL_PREFIX\\}")
+                (assoc-ref %build-inputs "clang")))
+             #t))
          (add-before 'configure 'set-LDFLAGS-and-CPATH
            (lambda* (#:key inputs outputs #:allow-other-keys)
              (setenv "LDFLAGS"
@@ -508,7 +516,8 @@ (define-public darktable
        ("glib:bin" ,glib "bin")
        ("gobject-introspection" ,gobject-introspection)
        ("intltool" ,intltool)
-       ("llvm" ,llvm)
+       ("llvm" ,llvm-9) ;should match the Clang version
+       ("opencl-headers" ,opencl-headers)
        ("perl" ,perl)
        ("pkg-config" ,pkg-config)
        ("po4a" ,po4a)))
@@ -520,6 +529,7 @@ (define-public darktable
        ("dbus-glib" ,dbus-glib)
        ("exiv2" ,exiv2)
        ("freeimage" ,freeimage)
+       ("gmic" ,gmic)
        ("graphicsmagick" ,graphicsmagick)
        ("gsettings-desktop-schemas" ,gsettings-desktop-schemas)
        ("gtk+" ,gtk+)
@@ -539,7 +549,7 @@ (define-public darktable
        ("libwebp" ,libwebp)
        ("libxml2" ,libxml2)
        ("libxslt" ,libxslt)
-       ("lua" ,lua)
+       ("lua" ,lua) ;for plugins
        ("openexr" ,openexr)
        ("openjpeg" ,openjpeg)
        ("osm-gps-map" ,osm-gps-map)