diff --git a/bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java b/bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
index 12e534ad85b..11e5cbfdf73 100644
--- a/bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
+++ b/bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
@@ -16,6 +16,7 @@
 
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.eclipse.core.runtime.IProgressMonitor;
@@ -1109,13 +1110,24 @@ private void hookZoomChangeListenerForDefaultSizedDialogs() {
 		}
 
 		AtomicReference<Listener> customResizeListener = new AtomicReference<>();
+		// setSize() sends the next SWT.Resize, which calls this listener again. Without the
+		// re-entrancy guard the listener recurses until the stack is exhausted whenever the
+		// computed size is not a fixed point, e.g. because a scrollbar appears and disappears
+		// with it.
+		AtomicBoolean adaptingDefaultSize = new AtomicBoolean();
 		Listener adaptDefaultSizeListener = event -> {
 			Shell shell = getShell();
-			if (shell == null || shell.isDisposed()) {
+			if (shell == null || shell.isDisposed() || !adaptingDefaultSize.compareAndSet(false, true)) {
 				return;
 			}
-			Point size = shell.computeSize(SWT.DEFAULT, SWT.DEFAULT, true);
-			shell.setSize(size);
+			try {
+				Point size = shell.computeSize(SWT.DEFAULT, SWT.DEFAULT, true);
+				if (!size.equals(shell.getSize())) {
+					shell.setSize(size);
+				}
+			} finally {
+				adaptingDefaultSize.set(false);
+			}
 		};
 		AtomicReference<Listener> zoomChangeListener = new AtomicReference<>();
 		zoomChangeListener.set(event -> {
diff --git a/bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java b/bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
index 562d5493509..6b83af04a29 100644
--- a/bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
+++ b/bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
@@ -342,6 +342,16 @@ public int getShellStyle() {
 		return super.getShellStyle();
 	}
 
+	/**
+	 * A wizard dialog is resizable unless a caller has stripped {@link SWT#RESIZE} from its shell
+	 * style, so the answer is read from that style instead of being inherited from
+	 * <code>Dialog</code>, which always answers <code>false</code>.
+	 */
+	@Override
+	protected boolean isResizable() {
+		return (getShellStyle() & SWT.RESIZE) != 0;
+	}
+
 	private static int getShellModality(boolean modal) {
 		return modal ? SWT.PRIMARY_MODAL : SWT.NONE;
 	}