diff --git a/CHANGES b/CHANGES
index 4e850e894..5b9835446 100644
--- a/CHANGES
+++ b/CHANGES
@@ -46,6 +46,7 @@ Bugs fixed
 * #2304: auto line breaks in latexpdf codeblocks
 * #1534: Word wrap long lines in Latex verbatim blocks
 * #2460: too much white space on top of captioned literal blocks in PDF output
+* Show error reason when multiple math extensions are loaded (ref: #2499)
 
 
 Release 1.4.1 (released Apr 12, 2016)
diff --git a/sphinx/ext/imgmath.py b/sphinx/ext/imgmath.py
index 40a9c1402..73a405ceb 100644
--- a/sphinx/ext/imgmath.py
+++ b/sphinx/ext/imgmath.py
@@ -22,7 +22,7 @@ from six import text_type
 from docutils import nodes
 
 import sphinx
-from sphinx.errors import SphinxError
+from sphinx.errors import SphinxError, ExtensionError
 from sphinx.util.png import read_png_depth, write_png_depth
 from sphinx.util.osutil import ensuredir, ENOENT, cd
 from sphinx.util.pycompat import sys_encoding
@@ -267,7 +267,11 @@ def html_visit_displaymath(self, node):
 
 
 def setup(app):
-    mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
+    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')
+
     app.add_config_value('imgmath_image_format', 'png', 'html')
     app.add_config_value('imgmath_dvipng', 'dvipng', 'html')
     app.add_config_value('imgmath_dvisvgm', 'dvisvgm', 'html')
diff --git a/sphinx/ext/mathjax.py b/sphinx/ext/mathjax.py
index 5d1f82408..43f28e376 100644
--- a/sphinx/ext/mathjax.py
+++ b/sphinx/ext/mathjax.py
@@ -15,6 +15,7 @@ from docutils import nodes
 
 import sphinx
 from sphinx.application import ExtensionError
+from sphinx.errors import ExtensionError
 from sphinx.ext.mathbase import setup_math as mathbase_setup
 
 
@@ -63,7 +64,11 @@ def builder_inited(app):
 
 
 def setup(app):
-    mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
+    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')
+
     # more information for mathjax secure url is here:
     # http://docs.mathjax.org/en/latest/start.html#secure-access-to-the-cdn
     app.add_config_value('mathjax_path',
@@ -72,4 +77,5 @@ def setup(app):
     app.add_config_value('mathjax_inline', [r'\(', r'\)'], 'html')
     app.add_config_value('mathjax_display', [r'\[', r'\]'], 'html')
     app.connect('builder-inited', builder_inited)
+
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/sphinx/ext/pngmath.py b/sphinx/ext/pngmath.py
index a2801bd1f..8707ca383 100644
--- a/sphinx/ext/pngmath.py
+++ b/sphinx/ext/pngmath.py
@@ -23,7 +23,7 @@ from six import text_type
 from docutils import nodes
 
 import sphinx
-from sphinx.errors import SphinxError
+from sphinx.errors import SphinxError, ExtensionError
 from sphinx.util.png import read_png_depth, write_png_depth
 from sphinx.util.osutil import ensuredir, ENOENT, cd
 from sphinx.util.pycompat import sys_encoding
@@ -239,7 +239,11 @@ def html_visit_displaymath(self, node):
 
 def setup(app):
     app.warn('sphinx.ext.pngmath has been deprecated. Please use sphinx.ext.imgmath instead.')
-    mathbase_setup(app, (html_visit_math, None), (html_visit_displaymath, None))
+    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')
+
     app.add_config_value('pngmath_dvipng', 'dvipng', 'html')
     app.add_config_value('pngmath_latex', 'latex', 'html')
     app.add_config_value('pngmath_use_preview', False, 'html')