diff --git a/NEWS b/NEWS
index e7bb8927b..b81d7e5d0 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,11 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2021-04-30:
+
+- Fixed a bug introduced on 2020-09-05 that caused "echo ${var:+'{}'}"
+  to be misparsed.
+
 2021-04-26:
 
 - Fixed a bug introduced on 2021-02-20 in which a shared-state command
diff --git a/src/cmd/ksh93/data/lexstates.c b/src/cmd/ksh93/data/lexstates.c
index 41344f3cc..2465e268a 100644
--- a/src/cmd/ksh93/data/lexstates.c
+++ b/src/cmd/ksh93/data/lexstates.c
@@ -387,6 +387,30 @@ static const char sh_lexstate9[256] =
 	0,	0,	0,	S_BRACE,S_PAT,	S_ENDCH,0,	0
 };
 
+/*
+ * ST_MOD1
+ * for skipping over a string S in ${v-S}, ${v+S}, ${v:-S}, ${v:+S}
+ */
+static const char sh_lexstate11[256] =
+{
+	S_EOF,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	S_NL,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	S_QUOTE,0,	S_DOL,	0,	0,	S_LIT,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	S_ESC,	0,	0,	0,
+	S_GRAVE,0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	0,	0,	0,
+	0,	0,	0,	0,	0,	S_RBRA,	0,	0
+};
+
 /*
  * This must be kept synchronous with all the above and the ST_* definitions in lexstates.h
  */
@@ -394,7 +418,7 @@ const char *sh_lexrstates[ST_NONE] =
 {
 	sh_lexstate0, sh_lexstate1, sh_lexstate2, sh_lexstate3,
 	sh_lexstate4, sh_lexstate5, sh_lexstate6, sh_lexstate7,
-	sh_lexstate8, sh_lexstate9, sh_lexstate5
+	sh_lexstate8, sh_lexstate9, sh_lexstate5, sh_lexstate11
 };
 
 
diff --git a/src/cmd/ksh93/include/lexstates.h b/src/cmd/ksh93/include/lexstates.h
index d1fbaee37..fb882a66e 100644
--- a/src/cmd/ksh93/include/lexstates.h
+++ b/src/cmd/ksh93/include/lexstates.h
@@ -79,7 +79,8 @@
 #define ST_DOLNAME	8
 #define ST_MACRO	9
 #define ST_QNEST	10
-#define ST_NONE		11
+#define ST_MOD1		11
+#define ST_NONE		12
 
 #include "FEATURE/locale"
 
diff --git a/src/cmd/ksh93/include/version.h b/src/cmd/ksh93/include/version.h
index 3de355fd9..b09b3e228 100644
--- a/src/cmd/ksh93/include/version.h
+++ b/src/cmd/ksh93/include/version.h
@@ -21,7 +21,7 @@
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
 #define SH_RELEASE_SVER	"1.0.0-alpha"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2021-04-26"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2021-04-30"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2021 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */
diff --git a/src/cmd/ksh93/sh/lex.c b/src/cmd/ksh93/sh/lex.c
index 14ef46ae8..a65f8fbe7 100644
--- a/src/cmd/ksh93/sh/lex.c
+++ b/src/cmd/ksh93/sh/lex.c
@@ -992,7 +992,7 @@ int sh_lex(Lex_t* lp)
 				mode = ST_NESTED;
 				continue;
 			case S_MOD1:
-				mode = ST_QUOTE;
+				mode = ST_MOD1;
 				continue;
 			case S_MOD2:
 #if SHOPT_KIA
diff --git a/src/cmd/ksh93/tests/quoting2.sh b/src/cmd/ksh93/tests/quoting2.sh
index 8fc4ce609..cab135481 100755
--- a/src/cmd/ksh93/tests/quoting2.sh
+++ b/src/cmd/ksh93/tests/quoting2.sh
@@ -250,5 +250,18 @@ actual=$(printf %q $'1\x[11]1')
 [[ $actual == "$expect" ]] || err_exit 'shell-quoting: hex bytes not protected from subsequent hex-like chars' \
 				"(expected $expect; got $actual)"
 
+# ======
+# https://github.com/ksh93/ksh/issues/290
+var=dummy
+exp='{}'
+got=$(eval 'echo ${var:+'\''{}'\''}' 2>&1)
+[[ $got == "$exp" ]] || err_exit "Single quotes misparsed in expansion operator string (1)" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+unset var
+exp='}'
+got=$(eval 'echo ${var:-'\''}'\''}' 2>&1)
+[[ $got == "$exp" ]] || err_exit "Single quotes misparsed in expansion operator string (2)" \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+
 # ======
 exit $((Errors<125?Errors:125))