diff --git a/engine/compiler.c b/engine/compiler.c
index 4d43c02..248cecf 100644
--- a/engine/compiler.c
+++ b/engine/compiler.c
@@ -4998,7 +4998,6 @@ static const LangConstruct aLangConstruct[] = {
 	{ PH7_KEYWORD_GOTO,     PH7_CompileGoto     }, /* goto statement */
 	{ PH7_KEYWORD_CONST,    PH7_CompileConstant }, /* const statement */
 	{ PH7_KEYWORD_INCLUDE,  PH7_CompileInclude  }, /* include statement */
-	{ PH7_KEYWORD_REQUIRE,  PH7_CompileInclude  }, /* require statement */
 };
 /*
  * Return a pointer to the global scope handler routine associated
diff --git a/engine/vfs.c b/engine/vfs.c
index 9610504..2d61690 100644
--- a/engine/vfs.c
+++ b/engine/vfs.c
@@ -3024,7 +3024,11 @@ PH7_PRIVATE void *PH7_StreamOpenHandle(ph7_vm *pVm, const ph7_io_stream *pStream
 		if(rc == PH7_OK) {
 			if(bPushInclude) {
 				/* Mark as included */
-				PH7_VmPushFilePath(pVm, sFilePath, -1, FALSE, pNew);
+				rc = PH7_VmPushFilePath(pVm, sFilePath, -1, FALSE, pNew);
+				if(rc != SXRET_OK) {
+					PH7_StreamCloseHandle(pStream, pHandle);
+					return 0;
+				}
 			}
 		}
 	} else {
diff --git a/engine/vm.c b/engine/vm.c
index f169ac4..d7be5b3 100644
--- a/engine/vm.c
+++ b/engine/vm.c
@@ -1507,6 +1507,10 @@ PH7_PRIVATE sxi32 PH7_VmInit(
 	SySetInit(&pVm->aFiles, &pVm->sAllocator, sizeof(SyString));
 	SySetInit(&pVm->aPaths, &pVm->sAllocator, sizeof(SyString));
 	SySetInit(&pVm->aIncluded, &pVm->sAllocator, sizeof(SyString));
+	rc = SyHashInit(&pVm->hRequired, &pVm->sAllocator, SyStrHash, (int (*)(const void *, const void *, sxu32))SyMemcmp);
+	if(rc != SXRET_OK) {
+		goto Err;
+	}
 	SySetInit(&pVm->aOB, &pVm->sAllocator, sizeof(VmObEntry));
 	SySetInit(&pVm->aIOstream, &pVm->sAllocator, sizeof(ph7_io_stream *));
 	/* Error callbacks containers */
@@ -2361,6 +2365,8 @@ PH7_PRIVATE sxi32 PH7_VmThrowError(
 		sxu32 nLine;
 		SyString sFileName;
 		SyString *pFile;
+		/* Included global code has no execution trace to populate this set. */
+		SySetInit(&pDebug, &pVm->sAllocator, sizeof(VmDebugTrace));
 		if((pVm->nMagic == PH7_VM_EXEC) && (VmExtractDebugTrace(&(*pVm), &pDebug) == SXRET_OK) && (SySetUsed(&pDebug) > 0)) {
 			/* Extract file name and line number from debug trace */
 			SySetGetNextEntry(&pDebug, (void **)&pTrace);
@@ -9329,11 +9335,17 @@ static sxi32 VmEvalChunk(
 	int iFlags          /* Code evaluation flag */
 ) {
 	SySet *pByteCode, aByteCode;
+	sxi32 rc = SXRET_OK;
+	sxi32 bRequire = (iFlags & (PH7_AERSCRIPT_CODE | PH7_AERSCRIPT_FILE)) ==
+		(PH7_AERSCRIPT_CODE | PH7_AERSCRIPT_FILE);
 	ProcConsumer xErr = 0;
 	void *pErrData = 0;
 	/* Initialize bytecode container */
 	SySetInit(&aByteCode, &pVm->sAllocator, sizeof(VmInstr));
-	SySetAlloc(&aByteCode, 0x20);
+	rc = SySetAlloc(&aByteCode, 0x20);
+	if(rc != SXRET_OK && bRequire) {
+		return rc;
+	}
 	/* Log compile-time errors */
 	xErr = pVm->pEngine->xConf.xErr;
 	pErrData = pVm->pEngine->xConf.pErrData;
@@ -9346,13 +9358,17 @@ static sxi32 VmEvalChunk(
 		PH7_VmPushFilePath(pVm, "[MEMORY]", -1, TRUE, 0);
 	}
 	/* Compile the chunk */
-	PH7_CompileAerScript(pVm, pChunk, iFlags);
+	rc = PH7_CompileAerScript(pVm, pChunk, iFlags);
+	if(rc != SXRET_OK && bRequire) {
+		goto Cleanup;
+	}
 	ph7_value sResult; /* Return value */
 	SyHashEntry *pEntry;
 	/* Initialize and install static and constants class attributes */
 	SyHashResetLoopCursor(&pVm->hClass);
 	while((pEntry = SyHashGetNextEntry(&pVm->hClass)) != 0) {
-		if(VmMountUserClass(&(*pVm), (ph7_class *)pEntry->pUserData) != SXRET_OK) {
+		rc = VmMountUserClass(&(*pVm), (ph7_class *)pEntry->pUserData);
+		if(rc != SXRET_OK) {
 			if(pCtx) {
 				ph7_result_bool(pCtx, 0);
 			}
@@ -9360,6 +9376,7 @@ static sxi32 VmEvalChunk(
 		}
 	}
 	if(SXRET_OK != PH7_VmEmitInstr(pVm, 0, PH7_OP_DONE, 0, 0, 0, 0)) {
+		rc = SXERR_MEM;
 		/* Out of memory */
 		if(pCtx) {
 			ph7_result_bool(pCtx, 0);
@@ -9369,7 +9386,7 @@ static sxi32 VmEvalChunk(
 	/* Assume a boolean true return value */
 	PH7_MemObjInitFromBool(pVm, &sResult, 1);
 	/* Execute the compiled chunk */
-	VmLocalExec(pVm, &aByteCode, &sResult);
+	rc = VmLocalExec(pVm, &aByteCode, &sResult);
 	if(pCtx) {
 		/* Set the execution result */
 		ph7_result_value(pCtx, &sResult);
@@ -9379,7 +9396,7 @@ Cleanup:
 	/* Cleanup the mess left behind */
 	pVm->pByteContainer = pByteCode;
 	SySetRelease(&aByteCode);
-	return SXRET_OK;
+	return bRequire ? rc : SXRET_OK;
 }
 /*
  * value eval(string $code)
@@ -9477,7 +9494,14 @@ PH7_PRIVATE sxi32 PH7_VmPushFilePath(ph7_vm *pVm, const char *zPath, int nLen, s
 			*pNew = 1;
 		}
 	}
-	SySetPut(&pVm->aFiles, (const void *)&sPath);
+	rc = SySetPut(&pVm->aFiles, (const void *)&sPath);
+	if(rc != SXRET_OK) {
+		if(!bMain && *pNew) {
+			SySetPop(&pVm->aIncluded);
+		}
+		SyMemBackendFree(&pVm->sAllocator, zDup);
+		return rc;
+	}
 	return SXRET_OK;
 }
 /*
@@ -9487,8 +9511,8 @@ PH7_PRIVATE sxi32 PH7_VmPushFilePath(ph7_vm *pVm, const char *zPath, int nLen, s
  * Note that the PHP script to evaluate can be a local or remote file.In
  * either cases the [PH7_StreamReadWholeFile()] function handle all the underlying
  * operations.
- * Refer to the implementation of the include(),include_once() language
- * constructs for more information.
+ * Include evaluates a method chunk; require evaluates global code once per VM,
+ * independently of the include history.
  */
 static sxi32 VmExecIncludedFile(
 	ph7_vm *pVm,       /* Underlying Virtual Machine */
@@ -9500,6 +9524,8 @@ static sxi32 VmExecIncludedFile(
 	SyBlob sContents;
 	void *pHandle;
 	int isNew;
+	SyString sRequired;
+	SyHashEntry *pRequired = 0;
 	/* Initialize fields */
 	SyBlobInit(&sContents, &pVm->sAllocator);
 	isNew = 0;
@@ -9514,21 +9540,44 @@ static sxi32 VmExecIncludedFile(
 		return SXERR_IO;
 	}
 	rc = SXRET_OK; /* Stupid cc warning */
-	if(iFlags & PH7_AERSCRIPT_CODE && !isNew) {
-		/* Already included (required) */
-		rc = SXERR_EXISTS;
-	} else {
-		/* Read the whole file contents */
-		rc = PH7_StreamReadWholeFile(pHandle, pStream, &sContents);
+	if(iFlags & PH7_AERSCRIPT_CODE) {
+		/* The loader owns these bytes until VM release. Do not use the spelling
+		 * from the statement, or the independent include history, as the key. */
+		sRequired = *(SyString *)SySetPeek(&pVm->aFiles);
+		pRequired = SyHashGet(&pVm->hRequired, sRequired.zString, sRequired.nByte);
+		if(pRequired) {
+			PH7_VmThrowError(pVm, PH7_CTX_WARNING, pRequired->pUserData ?
+				"File is already being required: '%z'" : "File already required: '%z'", &sRequired);
+			rc = SXERR_EXISTS;
+			goto Cleanup;
+		}
+		/* Publish before compilation/execution so recursive require cannot
+		 * redeclare the same file. Failed evaluations are not remembered. */
+		rc = SyHashInsert(&pVm->hRequired, sRequired.zString, sRequired.nByte, pVm);
+		if(rc != SXRET_OK) {
+			goto Cleanup;
+		}
+		pRequired = SyHashGet(&pVm->hRequired, sRequired.zString, sRequired.nByte);
+	}
+	/* Read the whole file contents */
+	rc = PH7_StreamReadWholeFile(pHandle, pStream, &sContents);
+	if(rc == SXRET_OK) {
+		SyString sScript;
+		sxu32 nMagic = pVm->nMagic;
+		/* Compile and execute the script */
+		SyStringInitFromBuf(&sScript, SyBlobData(&sContents), SyBlobLength(&sContents));
+		pVm->nMagic = PH7_VM_INCL;
+		rc = VmEvalChunk(pVm, 0, &sScript, iFlags);
+		pVm->nMagic = (iFlags & PH7_AERSCRIPT_CODE) ? nMagic : PH7_VM_EXEC;
+	}
+	if(pRequired) {
 		if(rc == SXRET_OK) {
-			SyString sScript;
-			/* Compile and execute the script */
-			SyStringInitFromBuf(&sScript, SyBlobData(&sContents), SyBlobLength(&sContents));
-			pVm->nMagic = PH7_VM_INCL;
-			VmEvalChunk(pVm, 0, &sScript, iFlags);
-			pVm->nMagic = PH7_VM_EXEC;
+			pRequired->pUserData = 0;
+		} else {
+			SyHashDeleteEntry(&pVm->hRequired, sRequired.zString, sRequired.nByte, 0);
 		}
 	}
+Cleanup:
 	/* Close the handle */
 	PH7_StreamCloseHandle(pStream, pHandle);
 	/* Release the working buffer */
diff --git a/include/ph7int.h b/include/ph7int.h
index 7c9e4fd..d1426a0 100644
--- a/include/ph7int.h
+++ b/include/ph7int.h
@@ -1208,6 +1208,7 @@ struct ph7_vm {
 	SySet aFiles;               /* Stack of processed files */
 	SySet aPaths;               /* Set of import paths */
 	SySet aIncluded;            /* Set of included files */
+	SyHash hRequired;           /* Resolved require paths, including pending evaluations */
 	SySet aOB;                  /* Stackable output buffers */
 	SySet aAutoLoad;			/* Stack of class autoload callbacks */
 	SySet aShutdown;            /* Stack of shutdown user callbacks */
diff --git a/tests/include_statements.aer b/tests/include_statements.aer
index 480099e..abf8883 100644
--- a/tests/include_statements.aer
+++ b/tests/include_statements.aer
@@ -1,10 +1,10 @@
 require 'data/includes/base_class.aer';
+require 'data/includes/test_class.aer';
 
 class Program extends BaseClass {
 
 	void main() {
 		$this->run();
-		require 'data/includes/test_class.aer';
 		object $test = new Test();
 		var_dump($test);
 	}