diff --git a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/domain-opacity/set.js b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/domain-opacity/set.js
index b61d3ef921a6..a0fd1e18c6ed 100644
--- a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/domain-opacity/set.js
+++ b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/domain-opacity/set.js
@@ -24,6 +24,7 @@
 
 var logger = require( 'debug' );
 var isBetween = require( '@stdlib/assert/is-between' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
 var format = require( '@stdlib/string/format' );
 var changeEvent = require( './../change_event.js' );
 var prop = require( './properties.js' );
@@ -45,7 +46,7 @@ var debug = logger( 'vega:axis:set:'+prop.name );
 * @returns {void}
 */
 function set( value ) {
-	if ( !isBetween( value, 0.0, 1.0 ) ) {
+	if ( !( isNumber( value ) && isBetween( value, 0.0, 1.0 ) ) ) {
 		throw new TypeError( format( 'invalid assignment. `%s` must be on the interval: [0, 1]. Value: `%s`.', prop.name, value ) );
 	}
 	if ( value !== this[ prop.private ] ) {
diff --git a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/grid-opacity/set.js b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/grid-opacity/set.js
index d80db2ab3380..5939b4a77053 100644
--- a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/grid-opacity/set.js
+++ b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/grid-opacity/set.js
@@ -24,6 +24,7 @@
 
 var logger = require( 'debug' );
 var isBetween = require( '@stdlib/assert/is-between' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
 var format = require( '@stdlib/string/format' );
 var changeEvent = require( './../change_event.js' );
 var prop = require( './properties.js' );
@@ -45,7 +46,7 @@ var debug = logger( 'vega:axis:set:'+prop.name );
 * @returns {void}
 */
 function set( value ) {
-	if ( !isBetween( value, 0.0, 1.0 ) ) {
+	if ( !( isNumber( value ) && isBetween( value, 0.0, 1.0 ) ) ) {
 		throw new TypeError( format( 'invalid assignment. `%s` must be on the interval: [0, 1]. Value: `%s`.', prop.name, value ) );
 	}
 	if ( value !== this[ prop.private ] ) {
diff --git a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/label-opacity/set.js b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/label-opacity/set.js
index 6bba5d146e68..043b693eeb68 100644
--- a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/label-opacity/set.js
+++ b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/label-opacity/set.js
@@ -24,6 +24,7 @@
 
 var logger = require( 'debug' );
 var isBetween = require( '@stdlib/assert/is-between' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
 var format = require( '@stdlib/string/format' );
 var changeEvent = require( './../change_event.js' );
 var prop = require( './properties.js' );
@@ -45,7 +46,7 @@ var debug = logger( 'vega:axis:set:'+prop.name );
 * @returns {void}
 */
 function set( value ) {
-	if ( !isBetween( value, 0.0, 1.0 ) ) {
+	if ( !( isNumber( value ) && isBetween( value, 0.0, 1.0 ) ) ) {
 		throw new TypeError( format( 'invalid assignment. `%s` must be on the interval: [0, 1]. Value: `%s`.', prop.name, value ) );
 	}
 	if ( value !== this[ prop.private ] ) {
diff --git a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/tick-opacity/set.js b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/tick-opacity/set.js
index f854341e5bc1..1fe05c225c6d 100644
--- a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/tick-opacity/set.js
+++ b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/tick-opacity/set.js
@@ -24,6 +24,7 @@
 
 var logger = require( 'debug' );
 var isBetween = require( '@stdlib/assert/is-between' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
 var format = require( '@stdlib/string/format' );
 var changeEvent = require( './../change_event.js' );
 var prop = require( './properties.js' );
@@ -45,7 +46,7 @@ var debug = logger( 'vega:axis:set:'+prop.name );
 * @returns {void}
 */
 function set( value ) {
-	if ( !isBetween( value, 0.0, 1.0 ) ) {
+	if ( !( isNumber( value ) && isBetween( value, 0.0, 1.0 ) ) ) {
 		throw new TypeError( format( 'invalid assignment. `%s` must be on the interval: [0, 1]. Value: `%s`.', prop.name, value ) );
 	}
 	if ( value !== this[ prop.private ] ) {
diff --git a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/title-opacity/set.js b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/title-opacity/set.js
index bb4698d77e39..be8130816b32 100644
--- a/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/title-opacity/set.js
+++ b/lib/node_modules/@stdlib/plot/vega/axis/ctor/lib/title-opacity/set.js
@@ -24,6 +24,7 @@
 
 var logger = require( 'debug' );
 var isBetween = require( '@stdlib/assert/is-between' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
 var format = require( '@stdlib/string/format' );
 var changeEvent = require( './../change_event.js' );
 var prop = require( './properties.js' );
@@ -45,7 +46,7 @@ var debug = logger( 'vega:axis:set:'+prop.name );
 * @returns {void}
 */
 function set( value ) {
-	if ( !isBetween( value, 0.0, 1.0 ) ) {
+	if ( !( isNumber( value ) && isBetween( value, 0.0, 1.0 ) ) ) {
 		throw new TypeError( format( 'invalid assignment. `%s` must be on the interval: [0, 1]. Value: `%s`.', prop.name, value ) );
 	}
 	if ( value !== this[ prop.private ] ) {