diff --git a/sphinx/ext/imgmath.py b/sphinx/ext/imgmath.py
index 3d1fa7537..307145adb 100644
--- a/sphinx/ext/imgmath.py
+++ b/sphinx/ext/imgmath.py
@@ -270,7 +270,7 @@ def setup(app):
     try:
         mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
     except ExtensionError:
-        raise ExtensionError('sphinx.ext.imgmath: other math package is already installed')
+        raise ExtensionError('sphinx.ext.imgmath: other math package is already loaded')
 
     app.add_config_value('imgmath_image_format', 'png', 'html')
     app.add_config_value('imgmath_dvipng', 'dvipng', 'html')
diff --git a/sphinx/ext/mathjax.py b/sphinx/ext/mathjax.py
index c95326bc8..bdaab55e0 100644
--- a/sphinx/ext/mathjax.py
+++ b/sphinx/ext/mathjax.py
@@ -66,7 +66,7 @@ def setup(app):
     try:
         mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
     except ExtensionError:
-        raise ExtensionError('sphinx.ext.mathjax: other math package is already installed')
+        raise ExtensionError('sphinx.ext.mathjax: other math package is already loaded')
 
     # more information for mathjax secure url is here:
     # http://docs.mathjax.org/en/latest/start.html#secure-access-to-the-cdn
diff --git a/sphinx/ext/pngmath.py b/sphinx/ext/pngmath.py
index 501064cc9..d7660550e 100644
--- a/sphinx/ext/pngmath.py
+++ b/sphinx/ext/pngmath.py
@@ -242,7 +242,7 @@ def setup(app):
     try:
         mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
     except ExtensionError:
-        raise ExtensionError('sphinx.ext.pngmath: other math package is already installed')
+        raise ExtensionError('sphinx.ext.pngmath: other math package is already loaded')
 
     app.add_config_value('pngmath_dvipng', 'dvipng', 'html')
     app.add_config_value('pngmath_latex', 'latex', 'html')