diff --git a/pkgs/applications/science/math/sage/patches/Only-test-py2-py3-optional-tests-when-all-of-sage-is.patch b/pkgs/applications/science/math/sage/patches/Only-test-py2-py3-optional-tests-when-all-of-sage-is.patch
new file mode 100644
index 00000000000..2a7dc13756d
--- /dev/null
+++ b/pkgs/applications/science/math/sage/patches/Only-test-py2-py3-optional-tests-when-all-of-sage-is.patch
@@ -0,0 +1,26 @@
+From c8edfefbbec87ca776d3cf84ee895aac200dda40 Mon Sep 17 00:00:00 2001
+From: Timo Kaufmann <timokau@zoho.com>
+Date: Sun, 21 Oct 2018 17:52:40 +0200
+Subject: [PATCH] Only test py2/py3 optional tests when all of sage is tested
+
+---
+ src/sage/doctest/control.py | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/src/sage/doctest/control.py b/src/sage/doctest/control.py
+index bf18df8b2b..b04af0e2e8 100644
+--- a/src/sage/doctest/control.py
++++ b/src/sage/doctest/control.py
+@@ -362,7 +362,8 @@ class DocTestController(SageObject):
+                     if not optionaltag_regex.search(o):
+                         raise ValueError('invalid optional tag {!r}'.format(o))
+ 
+-                options.optional |= auto_optional_tags
++                if "sage" in options.optional:
++                    options.optional |= auto_optional_tags
+ 
+         self.options = options
+ 
+-- 
+2.18.1
+
diff --git a/pkgs/applications/science/math/sage/sage-src.nix b/pkgs/applications/science/math/sage/sage-src.nix
index 942ee5f2200..b86f9d1aa0d 100644
--- a/pkgs/applications/science/math/sage/sage-src.nix
+++ b/pkgs/applications/science/math/sage/sage-src.nix
@@ -32,6 +32,11 @@ stdenv.mkDerivation rec {
     # case. For some yet unknown reason, that breaks the docbuild on nix and archlinux.
     # See https://groups.google.com/forum/#!msg/sage-packaging/VU4h8IWGFLA/mrmCMocYBwAJ.
     ./patches/revert-sphinx-always-fork.patch
+
+    # Make sure py2/py3 tests are only run when their expected context (all "sage"
+    # tests) are also run. That is necessary to test dochtml individually. See
+    # https://trac.sagemath.org/ticket/26110 for an upstream discussion.
+    ./patches/Only-test-py2-py3-optional-tests-when-all-of-sage-is.patch
   ];
 
   packageUpgradePatches = [