diff --git a/docs/source/building.rst b/docs/source/building.rst
index 25bfe069e..a7109b3f2 100644
--- a/docs/source/building.rst
+++ b/docs/source/building.rst
@@ -285,6 +285,15 @@ This happens when your program uses floating point values, and you forgot to imp
 If you use floating points, the compiler needs routines from that library.
 Fix it by adding an ``%import floats``.
 
+Gradle error when building the compiler yourself
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+If you get a gradle build error containing the line "No matching toolchains found for requested specification"
+somewhere, it means that the Gradle build tool can't locate the correct version of the JDK to use.
+The file "gradle.properties" contains a line like this: ``javaVersion=11``.
+You can do one of two things to fix the build error:
+
+- install a JDK with that version,
+- or change the version number to match the JDK version that *is* installed on your system (must be >= 11)
 
 
 Examples