diff --git a/OMCompiler/Compiler/NFFrontEnd/NFTyping.mo b/OMCompiler/Compiler/NFFrontEnd/NFTyping.mo
index 58a1050d782..4de9e583e9b 100644
--- a/OMCompiler/Compiler/NFFrontEnd/NFTyping.mo
+++ b/OMCompiler/Compiler/NFFrontEnd/NFTyping.mo
@@ -3091,6 +3091,12 @@ algorithm
     (cond, ty, var) := typeCondition(cond, context, source,
       Error.WHEN_CONDITION_TYPE_ERROR, allowVector = true, allowClock = true);
 
+    if var > Variability.IMPLICITLY_DISCRETE and not Type.isClock(ty) then
+      Error.addSourceMessage(Error.NON_DISCRETE_WHEN_CONDITION,
+        {Expression.toString(cond)}, ElementSource.getInfo(source));
+      fail();
+    end if;
+
     if not checkWhenInitial(cond) then
       Error.addSourceMessage(Error.INITIAL_CALL_WARNING,
           {Expression.toString(cond)}, ElementSource.getInfo(source));
diff --git a/OMCompiler/Compiler/Util/Error.mo b/OMCompiler/Compiler/Util/Error.mo
index b1b7e736855..f6d449c4e25 100644
--- a/OMCompiler/Compiler/Util/Error.mo
+++ b/OMCompiler/Compiler/Util/Error.mo
@@ -834,6 +834,8 @@ public constant ErrorTypes.Message MISSING_INNER_NAME_CONFLICT = ErrorTypes.MESS
   Gettext.gettext("An inner declaration for outer component ‘%s‘ could not be found, and could not be automatically generated due to a existing declaration of that name."));
 public constant ErrorTypes.Message TOP_LEVEL_INPUT_WITH_BINDING = ErrorTypes.MESSAGE(381, ErrorTypes.TRANSLATION(), ErrorTypes.NOTIFICATION(),
   Gettext.gettext("Top-level input ‘%s‘ has a binding equation and will not be accessible as an input of the model."));
+public constant ErrorTypes.Message NON_DISCRETE_WHEN_CONDITION = ErrorTypes.MESSAGE(382, ErrorTypes.TRANSLATION(), ErrorTypes.ERROR(),
+  Gettext.gettext("When-condition ‘%s‘ is not a discrete-time expression."));
 
 public constant ErrorTypes.Message INITIALIZATION_NOT_FULLY_SPECIFIED = ErrorTypes.MESSAGE(496, ErrorTypes.TRANSLATION(), ErrorTypes.WARNING(),
   Gettext.gettext("The initial conditions are not fully specified. %s."));
diff --git a/testsuite/flattening/modelica/scodeinst/Makefile b/testsuite/flattening/modelica/scodeinst/Makefile
index 2b516d60c87..fd03dea1e6b 100644
--- a/testsuite/flattening/modelica/scodeinst/Makefile
+++ b/testsuite/flattening/modelica/scodeinst/Makefile
@@ -913,6 +913,10 @@ WhenClockedElse1.mo \
 WhenClockedElse2.mo \
 WhenClockedStatement1.mo \
 WhenClockedTupleCall1.mo \
+WhenCondition1.mo \
+WhenCondition2.mo \
+WhenCondition3.mo \
+WhenCondition4.mo \
 WhenIllegalContext1.mo \
 WhenIllegalContext2.mo \
 WhenIllegalContext3.mo \
diff --git a/testsuite/flattening/modelica/scodeinst/WhenCondition1.mo b/testsuite/flattening/modelica/scodeinst/WhenCondition1.mo
new file mode 100644
index 00000000000..fe9ee92c806
--- /dev/null
+++ b/testsuite/flattening/modelica/scodeinst/WhenCondition1.mo
@@ -0,0 +1,26 @@
+// name: WhenCondition1
+// keywords:
+// status: correct
+// cflags:   -d=newInst
+//
+//
+
+model WhenCondition1
+  Boolean b;
+  Real x;
+equation
+  when b then
+    x = 1.0;
+  end when;
+end WhenCondition1;
+
+// Result:
+// class WhenCondition1
+//   Boolean b;
+//   Real x;
+// equation
+//   when b then
+//     x = 1.0;
+//   end when;
+// end WhenCondition1;
+// endResult
diff --git a/testsuite/flattening/modelica/scodeinst/WhenCondition2.mo b/testsuite/flattening/modelica/scodeinst/WhenCondition2.mo
new file mode 100644
index 00000000000..d976d49d0c9
--- /dev/null
+++ b/testsuite/flattening/modelica/scodeinst/WhenCondition2.mo
@@ -0,0 +1,26 @@
+// name: WhenCondition2
+// keywords:
+// status: correct
+// cflags:   -d=newInst
+//
+//
+
+model WhenCondition2
+  Boolean b;
+  Real x;
+equation
+  when {b, initial()} then
+    x = 1.0;
+  end when;
+end WhenCondition2;
+
+// Result:
+// class WhenCondition2
+//   Boolean b;
+//   Real x;
+// equation
+//   when {b, initial()} then
+//     x = 1.0;
+//   end when;
+// end WhenCondition2;
+// endResult
diff --git a/testsuite/flattening/modelica/scodeinst/WhenCondition3.mo b/testsuite/flattening/modelica/scodeinst/WhenCondition3.mo
new file mode 100644
index 00000000000..30326294a29
--- /dev/null
+++ b/testsuite/flattening/modelica/scodeinst/WhenCondition3.mo
@@ -0,0 +1,24 @@
+// name: WhenCondition3
+// keywords:
+// status: correct
+// cflags:   -d=newInst
+//
+//
+
+model WhenCondition3
+  Real x;
+equation
+  when time > 0 then
+    x = 1.0;
+  end when;
+end WhenCondition3;
+
+// Result:
+// class WhenCondition3
+//   Real x;
+// equation
+//   when time > 0.0 then
+//     x = 1.0;
+//   end when;
+// end WhenCondition3;
+// endResult
diff --git a/testsuite/flattening/modelica/scodeinst/WhenCondition4.mo b/testsuite/flattening/modelica/scodeinst/WhenCondition4.mo
new file mode 100644
index 00000000000..88360788726
--- /dev/null
+++ b/testsuite/flattening/modelica/scodeinst/WhenCondition4.mo
@@ -0,0 +1,24 @@
+// name: WhenCondition4
+// keywords:
+// status: incorrect
+// cflags:   -d=newInst
+//
+//
+
+model WhenCondition4
+  Real x;
+equation
+  when noEvent(time > 0) then
+    x = 1.0;
+  end when;
+end WhenCondition4;
+
+// Result:
+// Error processing file: WhenCondition4.mo
+// [flattening/modelica/scodeinst/WhenCondition4.mo:11:3-13:11:writable] Error: When-condition ‘noEvent(time > 0.0)‘ is not a discrete-time expression.
+//
+// # Error encountered! Exiting...
+// # Please check the error message and the flags.
+//
+// Execution failed!
+// endResult