diff --git a/configure.ac b/configure.ac
index 6dae0b9..d17629e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -548,10 +548,39 @@
 esac
 AM_CONDITIONAL([COND_THREADS], [test "x$enable_threads" != xno])
 
-# As a Debian-specific hack, liblzma uses dlopen() to check if extra
+# As a Debian-specific hack, liblzma can use dlopen() to check if extra
 # paranoia is needed because unversioned symbols from liblzma.so.2 are
 # present in the same process.  See src/liblzma/common/common.c.
-AC_SEARCH_LIBS([dlopen], [dl])
+AC_MSG_CHECKING([if lzma_code checks should be relaxed for compatibility])
+AC_ARG_ENABLE([liblzma2-compat], [AC_HELP_STRING([--enable-liblzma2-compat],
+		[Relax run-time checks to accomodate old binaries built
+		with smaller sizeof(lzma_stream).  The default is "dynamic",
+		which means to only use the relaxed checks when the dynamic
+		loader reports that liblzma.so.2 is loaded in the same process.])],
+	[], [enable_liblzma2_compat=dynamic])
+case $enable_liblzma2_compat in
+dynamic)
+	AC_SEARCH_LIBS([dlopen], [dl])
+	AC_DEFINE([LIBLZMA2_COMPAT_DYNAMIC], [1],
+		[Define to 1 to use dlopen() to check if lzma_code() checks
+		should be more tolerant because the process is also linked to
+		liblzma from Debian 6.0.])
+	AC_MSG_RESULT([auto])
+	;;
+yes)
+	AC_DEFINE([LIBLZMA2_COMPAT], [1],
+		[Define to 1 to unconditionally make lzma_code() checks tolerant
+		to accomodate callers built against liblzma from Debian 6.0.])
+	AC_MSG_RESULT([yes])
+	;;
+no)
+	AC_MSG_RESULT([no])
+	;;
+*)
+	AC_MSG_RESULT([])
+	AC_MSG_ERROR([--enable-liblzma2: unrecognized value $enable_liblzma2_compat])
+	;;
+esac
 
 echo
 echo "Initializing Libtool:"
diff --git a/src/liblzma/common/common.c b/src/liblzma/common/common.c
index 5474211..79427b0 100644
--- a/src/liblzma/common/common.c
+++ b/src/liblzma/common/common.c
@@ -164,16 +164,46 @@
 // External to internal API wrapper //
 //////////////////////////////////////
 
-static bool
-liblzma2_loaded(void)
+#ifdef LIBLZMA2_COMPAT_DYNAMIC
+
+static void
+init_liblzma2_compat(lzma_stream *strm)
 {
 	void *handle = dlopen("liblzma.so.2", RTLD_LAZY | RTLD_NOLOAD);
 	if (handle) {
 		dlclose(handle);
-		return true;
+		strm->internal->liblzma2_compat = true;
+		return;
 	}
+	strm->internal->liblzma2_compat = false;
+}
+
+static bool
+liblzma2_loaded(lzma_stream *strm)
+{
+	return strm->internal->liblzma2_compat;
+}
+
+#else
+
+static void
+init_liblzma2_compat(lzma_stream *strm)
+{
+}
+
+#ifdef LIBLZMA2_COMPAT
+static bool liblzma2_loaded(lzma_stream *strm)
+{
+	return true;
+}
+#else
+static bool liblzma2_loaded(lzma_stream *strm)
+{
 	return false;
 }
+#endif
+
+#endif
 
 extern lzma_ret
 lzma_strm_init(lzma_stream *strm)
@@ -188,7 +218,7 @@
 			return LZMA_MEM_ERROR;
 
 		strm->internal->next = LZMA_NEXT_CODER_INIT;
-		strm->internal->liblzma2_compat = liblzma2_loaded();
+		init_liblzma2_compat(strm);
 	}
 
 	memzero(strm->internal->supported_actions,
@@ -241,7 +271,7 @@
 			|| strm->reserved_ptr4 != NULL)
 		return LZMA_OPTIONS_ERROR;
 
-	if (strm->internal->liblzma2_compat)
+	if (liblzma2_loaded(strm))
 		; /* Enough checks. */
 	else if (strm->reserved_int1 != 0
 			|| strm->reserved_int2 != 0
diff --git a/src/liblzma/common/common.h b/src/liblzma/common/common.h
index b056e41..eb1d052 100644
--- a/src/liblzma/common/common.h
+++ b/src/liblzma/common/common.h
@@ -227,9 +227,11 @@
 	/// made (no input consumed and no output produced by next.code).
 	bool allow_buf_error;
 
+#ifdef LIBLZMA2_COMPAT_DYNAMIC
 	/// Indicates whether we are sharing a process image with
 	/// liblzma.so.2 and need to tread carefully.
 	bool liblzma2_compat;
+#endif
 };