diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index e222ef7..019be5d 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -3689,19 +3689,13 @@
     DCHECK(!IsStaticWithExplicitClinitCheck());
   }
 
-  HNewInstance* GetThisArgumentOfStringInit() const {
+  HInstruction* GetAndRemoveThisArgumentOfStringInit() {
     DCHECK(IsStringInit());
     size_t index = InputCount() - 1;
-    DCHECK(InputAt(index)->IsNewInstance());
-    return InputAt(index)->AsNewInstance();
-  }
-
-  void RemoveThisArgumentOfStringInit() {
-    DCHECK(IsStringInit());
-    size_t index = InputCount() - 1;
-    DCHECK(InputAt(index)->IsNewInstance());
+    HInstruction* input = InputAt(index);
     RemoveAsUserOfInput(index);
     inputs_.pop_back();
+    return input;
   }
 
   // Is this a call to a static method whose declaring class has an
diff --git a/compiler/optimizing/ssa_builder.cc b/compiler/optimizing/ssa_builder.cc
index c0011cd..c8244aa 100644
--- a/compiler/optimizing/ssa_builder.cc
+++ b/compiler/optimizing/ssa_builder.cc
@@ -927,16 +927,21 @@
   if (invoke->IsStringInit()) {
     // This is a StringFactory call which acts as a String constructor. Its
     // result replaces the empty String pre-allocated by NewInstance.
-    HNewInstance* new_instance = invoke->GetThisArgumentOfStringInit();
-    invoke->RemoveThisArgumentOfStringInit();
+    HInstruction* arg_this = invoke->GetAndRemoveThisArgumentOfStringInit();
 
     // Replacing the NewInstance might render it redundant. Keep a list of these
     // to be visited once it is clear whether it is has remaining uses.
-    uninitialized_strings_.push_back(new_instance);
+    if (arg_this->IsNewInstance()) {
+      uninitialized_strings_.push_back(arg_this->AsNewInstance());
+    } else {
+      DCHECK(arg_this->IsIrreducibleLoopHeaderPhi());
+      // NewInstance is not the direct input of the StringFactory call. It might
+      // be redundant but optimizing this case is not worth the effort.
+    }
 
-    // Walk over all vregs and replace any occurrence of `new_instance` with `invoke`.
+    // Walk over all vregs and replace any occurrence of `arg_this` with `invoke`.
     for (size_t vreg = 0, e = current_locals_->size(); vreg < e; ++vreg) {
-      if ((*current_locals_)[vreg] == new_instance) {
+      if ((*current_locals_)[vreg] == arg_this) {
         (*current_locals_)[vreg] = invoke;
       }
     }
diff --git a/test/563-checker-fakestring/smali/TestCase.smali b/test/563-checker-fakestring/smali/TestCase.smali
index 4bd804d..823ed1e 100644
--- a/test/563-checker-fakestring/smali/TestCase.smali
+++ b/test/563-checker-fakestring/smali/TestCase.smali
@@ -124,3 +124,31 @@
    return-object v0
 
 .end method
+
+# Test that the compiler does not assume that the first argument of String.<init>
+# is a NewInstance by inserting an irreducible loop between them (b/26676472).
+
+## CHECK-START-DEBUGGABLE: java.lang.String TestCase.thisNotNewInstance(byte[], boolean) register (after)
+## CHECK-DAG:                   InvokeStaticOrDirect env:[[<<Phi:l\d+>>,{{.*]]}}
+## CHECK-DAG:     <<Phi>>       Phi
+
+.method public static thisNotNewInstance([BZ)Ljava/lang/String;
+   .registers 5
+
+   new-instance v0, Ljava/lang/String;
+
+   # Irreducible loop
+   if-eqz p1, :loop_entry
+   :loop_header
+   const v1, 0x1
+   xor-int p1, p1, v1
+   :loop_entry
+   if-eqz p1, :string_init
+   goto :loop_header
+
+   :string_init
+   const-string v1, "UTF8"
+   invoke-direct {v0, p0, v1}, Ljava/lang/String;-><init>([BLjava/lang/String;)V
+   return-object v0
+
+.end method
diff --git a/test/563-checker-fakestring/src/Main.java b/test/563-checker-fakestring/src/Main.java
index 04df0f6..5489a0d 100644
--- a/test/563-checker-fakestring/src/Main.java
+++ b/test/563-checker-fakestring/src/Main.java
@@ -63,5 +63,13 @@
       String result = (String) m.invoke(null, new Object[] { testData });
       assertEqual(testString, result);
     }
+
+    {
+      Method m = c.getMethod("thisNotNewInstance", byte[].class, boolean.class);
+      String result = (String) m.invoke(null, new Object[] { testData, true });
+      assertEqual(testString, result);
+      result = (String) m.invoke(null, new Object[] { testData, false });
+      assertEqual(testString, result);
+    }
   }
 }