diff --git a/org.omg.sysml.interactive.tests/src/org/omg/sysml/interactive/tests/MultiplicityPreparationTest.java b/org.omg.sysml.interactive.tests/src/org/omg/sysml/interactive/tests/MultiplicityPreparationTest.java
index 6452238e8..39c50a0a9 100644
--- a/org.omg.sysml.interactive.tests/src/org/omg/sysml/interactive/tests/MultiplicityPreparationTest.java
+++ b/org.omg.sysml.interactive.tests/src/org/omg/sysml/interactive/tests/MultiplicityPreparationTest.java
@@ -155,9 +155,10 @@ public void explicitSpecializationsReceiveDefaultMultiplicity() throws Exception
 					attribute plainValues;
 				}
 				""");
-		for (String name : List.of("redefinedValues", "subsetValues", "chainValues", "packageValues")) {
+		for (String name : List.of("plainValues", "subsetValues", "chainValues", "packageValues")) {
 			Usage usage = findByName(resource, name, Usage.class);
-			// ST6RI-774 allows the default even when the target has [0..*].
+			// Allows the default even when the target has [0..*].
+			// TODO: Update as necessary after final resolution of SYSML21-185.
 			assertEquals(name, 1, TypeUtil.getOwnedMultiplicitiesOf(usage).size());
 			Multiplicity multiplicity = TypeUtil.getOwnedMultiplicitiesOf(usage).get(0);
 			assertEquals(SysMLPackage.Literals.MULTIPLICITY, multiplicity.eClass());
@@ -165,13 +166,14 @@ public void explicitSpecializationsReceiveDefaultMultiplicity() throws Exception
 			SysMLParserPostProcessorFactory.getPostProcessor(usage).postProcess();
 			assertEquals(name, 1, TypeUtil.getOwnedMultiplicitiesOf(usage).size());
 		}
-		assertEquals(1, TypeUtil.getOwnedMultiplicitiesOf(findByName(resource, "plainValues", Usage.class)).size());
+		assertTrue("redefinedValues", TypeUtil.getOwnedMultiplicitiesOf(findByName(resource, "redefinedValues", Usage.class)).isEmpty());
 
 		// Explicit transformation must retain the same multiplicity choices.
 		ElementUtil.transformAll(resource, true);
-		for (String name : List.of("redefinedValues", "subsetValues", "chainValues", "packageValues")) {
+		for (String name : List.of("plainValues", "subsetValues", "chainValues", "packageValues")) {
 			assertEquals(name, 1, TypeUtil.getOwnedMultiplicitiesOf(findByName(resource, name, Usage.class)).size());
 		}
+		assertTrue("redefinedValues", TypeUtil.getOwnedMultiplicitiesOf(findByName(resource, "redefinedValues", Usage.class)).isEmpty());
 	}
 
 	/**
diff --git a/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.63.0-SNAPSHOT.jar b/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.63.0-SNAPSHOT.jar
index 9f62f5b33..d8b0f57c9 100644
Binary files a/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.63.0-SNAPSHOT.jar and b/org.omg.sysml.logic.bundle/lib/org.omg.sysml.logic-0.63.0-SNAPSHOT.jar differ
diff --git a/org.omg.sysml.xtext/src/org/omg/sysml/xtext/postprocessing/UsageParserPostProcessor.java b/org.omg.sysml.xtext/src/org/omg/sysml/xtext/postprocessing/UsageParserPostProcessor.java
index eb64fc35d..5117e8da6 100644
--- a/org.omg.sysml.xtext/src/org/omg/sysml/xtext/postprocessing/UsageParserPostProcessor.java
+++ b/org.omg.sysml.xtext/src/org/omg/sysml/xtext/postprocessing/UsageParserPostProcessor.java
@@ -18,6 +18,7 @@
 import org.omg.kerml.xtext.postprocessing.FeatureParserPostProcessor;
 import org.omg.sysml.lang.sysml.AttributeDefinition;
 import org.omg.sysml.lang.sysml.AttributeUsage;
+import org.omg.sysml.lang.sysml.Redefinition;
 import org.omg.sysml.lang.sysml.SysMLPackage;
 import org.omg.sysml.lang.sysml.Type;
 import org.omg.sysml.lang.sysml.Usage;
@@ -82,16 +83,28 @@ protected void setIsVariableIfConstant() {
 	}
 
 	/**
-	 * Checks the owning type for eligible attribute, item and port usages.
-	 * Subsettings and redefinitions do not restrict this default (ST6RI-774);
-	 * their targets are not consulted. End usages always receive the default.
+	 * Check whether a default multiplicity should be added.
+	 * For use by attribute, item and port post-processor subclasses.
+	 * Usages with explicit owned redefinitions do not get a default,
+	 * except that end usages always receive the default.
+	 * 
+	 * TODO: Update as necessary after final resolution of SYSML21-185.
 	 */
 	protected boolean isAddDefaultMultiplicity() {
 		Usage target = getTarget();
-		return target.isEnd() || target.getOwningType() != null;
+		return target.isEnd() || 
+			   target.getOwningType() != null &&
+			   target.getOwnedRelationship().stream().
+			   		filter(rel->!rel.isImplied()).
+			   		noneMatch(Redefinition.class::isInstance);
 	}
 
-	// Multiplicity of 1..1 is always the default for an end usage.
+	/**
+	 * Check if a default multiplicity must be added to the usage.
+	 * Multiplicity of 1..1 is always the default for an end usage.
+	 * This method is overridden to call isAddDefaultMultiplicity in
+	 * the post-processors for kinds of usages that have defaults.
+	 */
 	protected boolean isAddMultiplicity() {
 		return getTarget().isEnd();
 	}