Document ImportWarning
diff --git a/Doc/lib/libexcs.tex b/Doc/lib/libexcs.tex
index 150f38d..bef8bf1 100644
--- a/Doc/lib/libexcs.tex
+++ b/Doc/lib/libexcs.tex
@@ -451,6 +451,11 @@
 in the future.
 \end{excdesc}
 
+\begin{excdesc}{ImportWarning}
+Base class for warnings about probable mistakes in module imports.
+\versionadded{2.5}
+\end{excdesc}
+
 The class hierarchy for built-in exceptions is:
 
 \verbatiminput{../../Lib/test/exception_hierarchy.txt}