diff --git a/WHATSNEW b/WHATSNEW
index e4d6fec74..c383573f7 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -70,6 +70,9 @@ Fixed bugs:
 
 * handle null result of system getProperty(). Bugzilla 42334.
 
+* Regression: concat fixlastline="true" should not have applied to
+  nested text, but did in Ant 1.7.0. Bugzilla 42369.
+
 Other changes:
 --------------
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/Concat.java b/src/main/org/apache/tools/ant/taskdefs/Concat.java
index 5b3c27535..6752af52a 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Concat.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Concat.java
@@ -265,7 +265,7 @@ public class Concat extends Task implements ResourceCollection {
                 int ch = getReader().read();
                 if (ch == -1) {
                     nextReader();
-                    if (fixLastLine && isMissingEndOfLine()) {
+                    if (isFixLastLine() && isMissingEndOfLine()) {
                         needAddSeparator = true;
                         lastPos = 0;
                     }
@@ -307,12 +307,12 @@ public class Concat extends Task implements ResourceCollection {
                 int nRead = getReader().read(cbuf, off, len);
                 if (nRead == -1 || nRead == 0) {
                     nextReader();
-                    if (fixLastLine && isMissingEndOfLine()) {
+                    if (isFixLastLine() && isMissingEndOfLine()) {
                         needAddSeparator = true;
                         lastPos = 0;
                     }
                 } else {
-                    if (fixLastLine) {
+                    if (isFixLastLine()) {
                         for (int i = nRead;
                                  i > (nRead - lastChars.length);
                                  --i) {
@@ -369,6 +369,10 @@ public class Concat extends Task implements ResourceCollection {
             }
             return false;
         }
+
+        private boolean isFixLastLine() {
+            return fixLastLine && textBuffer == null;
+        }
     }
 
     private class ConcatResource extends Resource {
@@ -887,10 +891,8 @@ public class Concat extends Task implements ResourceCollection {
      * for &quot;ignorable whitespace&quot; as well.</p>
      */
     private void sanitizeText() {
-        if (textBuffer != null) {
-            if (textBuffer.substring(0).trim().length() == 0) {
-                textBuffer = null;
-            }
+        if (textBuffer != null && "".equals(textBuffer.toString().trim())) {
+            textBuffer = null;
         }
     }
 
diff --git a/src/tests/antunit/taskdefs/concat-test.xml b/src/tests/antunit/taskdefs/concat-test.xml
index febe4a214..f4b13a2cb 100644
--- a/src/tests/antunit/taskdefs/concat-test.xml
+++ b/src/tests/antunit/taskdefs/concat-test.xml
@@ -1,4 +1,6 @@
-<project xmlns:au="antlib:org.apache.ant.antunit">
+<project default="antunit" xmlns:au="antlib:org.apache.ant.antunit">
+  <import file="../antunit-base.xml" />
+
   <target name="tearDown">
     <delete file="binaryAppendDest" />
     <delete file="encodeStringDest" />
@@ -35,4 +37,13 @@
     </au:assertTrue>
   </target>
 
+  <target name="testDoNotFixNestedText" description="Bugzilla 42369">
+    <au:assertTrue>
+      <resourcesmatch>
+        <string>foo</string>
+        <concat fixlastline="true">foo</concat>
+      </resourcesmatch>
+    </au:assertTrue>
+  </target>
+
 </project>