diff --git a/configure.ac b/configure.ac
index 53ae7be..6dae0b9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -548,6 +548,11 @@
 esac
 AM_CONDITIONAL([COND_THREADS], [test "x$enable_threads" != xno])
 
+# As a Debian-specific hack, liblzma uses 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])
+
 echo
 echo "Initializing Libtool:"
 LT_PREREQ([2.2])
diff --git a/src/liblzma/common/common.c b/src/liblzma/common/common.c
index 28aa2b7..5474211 100644
--- a/src/liblzma/common/common.c
+++ b/src/liblzma/common/common.c
@@ -12,6 +12,8 @@
 
 #include "common.h"
 
+#include <dlfcn.h>
+
 
 /////////////
 // Version //
@@ -162,6 +164,17 @@
 // External to internal API wrapper //
 //////////////////////////////////////
 
+static bool
+liblzma2_loaded(void)
+{
+	void *handle = dlopen("liblzma.so.2", RTLD_LAZY | RTLD_NOLOAD);
+	if (handle) {
+		dlclose(handle);
+		return true;
+	}
+	return false;
+}
+
 extern lzma_ret
 lzma_strm_init(lzma_stream *strm)
 {
@@ -175,6 +188,7 @@
 			return LZMA_MEM_ERROR;
 
 		strm->internal->next = LZMA_NEXT_CODER_INIT;
+		strm->internal->liblzma2_compat = liblzma2_loaded();
 	}
 
 	memzero(strm->internal->supported_actions,
@@ -189,6 +203,24 @@
 }
 
 
+// Before v5.0.0~6 (liblzma: A few ABI tweaks to reserve space in
+// structures, 2010-10-23), the reserved fields in lzma_stream were:
+//
+//	void *reserved_ptr1;
+//	void *reserved_ptr2;
+//	uint64_t reserved_int1;
+//	uint64_t reserved_int2;
+//	lzma_reserved_enum reserved_enum1;
+//	lzma_reserved_enum reserved_enum2;
+//
+// Nowadays there are two more pointers between reserved_ptr2 and
+// reserved_int1 and two size_t fields between reserved_int2 and
+// reserved_enum1.
+//
+// When strm->internal->liblzma2_compat is set, limit the checks of
+// reserved fields to fields that were present in the old ABI to avoid
+// segfaults and spurious "Unsupported options" from callers sharing
+// the process image that expect the old ABI.
 extern LZMA_API(lzma_ret)
 lzma_code(lzma_stream *strm, lzma_action action)
 {
@@ -206,8 +238,12 @@
 	if (strm->reserved_ptr1 != NULL
 			|| strm->reserved_ptr2 != NULL
 			|| strm->reserved_ptr3 != NULL
-			|| strm->reserved_ptr4 != NULL
-			|| strm->reserved_int1 != 0
+			|| strm->reserved_ptr4 != NULL)
+		return LZMA_OPTIONS_ERROR;
+
+	if (strm->internal->liblzma2_compat)
+		; /* Enough checks. */
+	else if (strm->reserved_int1 != 0
 			|| strm->reserved_int2 != 0
 			|| strm->reserved_int3 != 0
 			|| strm->reserved_int4 != 0
diff --git a/src/liblzma/common/common.h b/src/liblzma/common/common.h
index 955d784..b056e41 100644
--- a/src/liblzma/common/common.h
+++ b/src/liblzma/common/common.h
@@ -226,6 +226,10 @@
 	/// If true, lzma_code will return LZMA_BUF_ERROR if no progress was
 	/// made (no input consumed and no output produced by next.code).
 	bool allow_buf_error;
+
+	/// Indicates whether we are sharing a process image with
+	/// liblzma.so.2 and need to tread carefully.
+	bool liblzma2_compat;
 };